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Exhibit 99.3

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

        On September 3, 2002, Investment Technology Group, Inc. ("ITG") completed the acquisition of Hoenig Group Inc. ("Hoenig"). Under the revised terms of the agreement dated July 2, 2002, Hoenig stockholders received approximately $105.0 million, or $11.58 per share, of which approximately $2.4 million, or $0.23 per share, has been placed into an escrow account. Such escrow requirement relates to the pursuit, on behalf of Hoenig's shareholders, of certain insurance and other claims in connection with a $7.2 million pre-tax loss announced by Hoenig Group Inc. on May 9, 2002 as a result of unauthorized trading in foreign securities, by a former employee of Hoenig & Company Limited, in violation of Hoenig's policies and procedures.

        The unaudited pro forma condensed combined financial information (the "Pro Forma Information") is based on, derived from, and should be read in conjunction with the historical financial statements and notes thereto of both ITG and Hoenig as of June 30, 2002, for the year ended December 31, 2001, and for the six-month periods ended June 30, 2002 and 2001, respectively.

        The Pro Forma Information is presented for illustrative purposes only and is not necessarily indicative of the operating results that would have occurred or financial position if the acquisition of Hoenig had been consummated during the periods or as of the date for which the Pro Forma Information is presented, nor is it necessarily indicative of the future operating results or financial position of the combined company.

        The Pro Forma Information is based on available information and certain assumptions and adjustments as described in the notes thereto, which management believes is reasonable under the circumstances. There have been no transactions between ITG and Hoenig requiring adjustment in the Pro Forma Information.

        The following represents the unaudited pro forma condensed combined statements of income for the year ended December 31, 2001 and for the six-month periods ended June 30, 2002 and 2001, respectively, as if the acquisition of Hoenig had occurred at the beginning of each of the periods

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presented, as well as the unaudited pro forma condensed combined statement of financial condition as of June 30, 2002 (in thousands, except share and per share data):

        Unaudited Pro Forma Condensed Combined Statement of Income for the year ended December 31, 2001:

				ITG (historical)			Hoenig (historical)		Pro Forma Adjustments			Pro Forma Combined
				[a]			[b]		[d] [e] [f]
Revenues:
	Commissions:
		POSIT		$	186,101			—		—		$	186,101
		Electronic Trading Desk			89,748		$	93,508	$	(45,273	)		137,983
		Client Site Direct Access			93,993			—		—			93,993
	Other				7,565			4,750		(6,131	)		6,184
			Total revenues		377,407			98,258		(51,404	)		424,261
Expenses:
	Compensation and employee benefits				103,745			20,830		—			124,575
	Transaction processing				49,531			10,823		—			60,354
	Software royalties				23,726			—		—			23,726
	Occupancy and equipment				20,638			—		2,054			22,692
	Telecommunications and data processing services				15,086			—		3,097			18,183
	Independent research and other				—			45,786		(45,786	)		—
	Net (gain) loss on long-term investments				(309	)		9,292		(1,871	)		7,112
	Other general and administrative				28,878			10,586		(5,920	)		33,544
			Total expenses		241,295			97,317		(48,426	)		290,186
Income (loss) before income tax expense					136,112			941		(2,978	)		134,075
Income tax expense (benefit)					57,217			273		(1,200	)		56,290
Net income (loss)				$	78,895		$	668	$	(1,778	)	$	77,785
Earnings per share(1):
Basic				$	1.65							$	1.62
Diluted				$	1.62							$	1.60
Basic weighted average number of common shares outstanding					47,886					—			47,886
Diluted weighted average number of common shares outstanding					48,689					23			48,712

(1)

Earnings per share have been retroactively restated to reflect a three-for-two stock split in December 2001.

See Notes to Unaudited Pro Forma Condensed Combined Financial Information

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        Unaudited Pro Forma Condensed Combined Statement of Income for the six months ended June 30, 2002:

				ITG (historical)		Hoenig (historical)			Pro Forma Adjustments			Pro Forma Combined
				[a]		[b]			[c] [d] [e] [f]
Revenues:
	Commissions:
		POSIT		$	88,186		—			—		$	88,186
		Electronic Trading Desk			46,916	$	50,320		$	(26,879	)		70,357
		Client Site Direct Access			57,422		—			—			57,422
	Other				4,612		777			(823	)		4,566
			Total revenues		197,136		51,097			(27,702	)		220,531
Expenses:
	Compensation and employee benefits				55,635		10,091			—			65,726
	Transaction processing				23,572		5,655			—			29,227
	Software royalties				11,308		—			—			11,308
	Occupancy and equipment				13,132		—			1,144			14,276
	Telecommunications and data processing services				8,286		—			1,631			9,917
	Independent research and other				—		27,706			(27,706	)		—
	Loss including expenses from Hoenig & Company Limited				—		7,692			—			7,692
	Other general and administrative				11,633		6,403			(3,432	)		14,604
			Total expenses		123,566		57,547			(28,363	)		152,750
Income (loss) before income tax expense					73,570		(6,450	)		661			67,781
Income tax expense (benefit)					30,601		(420	)		255			30,436
Net income (loss)				$	42,969	$	(6,030	)	$	406		$	37,345
Earnings per share:
Basic				$	0.88							$	0.76
Diluted				$	0.87							$	0.75
Basic weighted average number of common shares outstanding					48,917					—			48,917
Diluted weighted average number of common shares outstanding					49,659					29			49,688

See Notes to Unaudited Pro Forma Condensed Combined Financial Information

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        Unaudited Pro Forma Condensed Combined Statement of Income for the six months ended June 30, 2001:

				ITG (historical)			Hoenig (historical)			Pro Forma Adjustments			Pro Forma Combined
				[a]			[b]			[d] [e] [f]
Revenues:
	Commissions:
		POSIT		$	90,524			—			—		$	90,524
		Electronic Trading Desk			42,100		$	45,674		$	(22,257	)		65,517
		Client Site Direct Access			48,250			—			—			48,250
	Other				5,715			3,263			(4,823	)		4,155
			Total revenues		186,589			48,937			(27,080	)		208,446
Expenses:
	Compensation and employee benefits				49,543			9,588			—			59,131
	Transaction processing				25,876			5,160			—			31,036
	Software royalties				11,629			—			—			11,629
	Occupancy and equipment				9,821			—			1,095			10,916
	Telecommunications and data processing services				7,131			—			1,430			8,561
	Independent research and other				—			23,048			(23,048	)		—
	Net (gain) loss on long-term investments				(309	)		9,292			(1,543	)		7,440
	Other general and administrative				13,627			5,369			(3,195	)		15,801
			Total expenses		117,318			52,457			(25,261	)		144,514
Income (loss) before income tax expense					69,271			(3,520	)		(1,819	)		63,932
Income tax expense (benefit)					29,149			(1,566	)		(742	)		26,841
Net income (loss)				$	40,122		$	(1,954	)	$	(1,077	)	$	37,091
Earnings per share(1):
Basic				$	0.84								$	0.78
Diluted				$	0.83								$	0.77
Basic weighted average number of common shares outstanding					47,571						—			47,571
Diluted weighted average number of common shares outstanding					48,312						21			48,333

(1)

Earnings per share have been retroactively restated to reflect a three-for-two stock split in December 2001.

See Notes to Unaudited Pro Forma Condensed Combined Financial Information

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        Unaudited Pro Forma Condensed Combined Statement of Financial Condition as of June 30, 2002:

			ITG (historical)			Hoenig (historical)			Pro Forma Adjustments			Pro Forma Combined
			[a]			[b]			[g]
Assets
Cash and cash equivalents			$	253,632		$	37,518		$	(103,706	)	$	187,444
Securities owned, at fair value				67,346			14,566			—			81,912
Receivables from brokers, dealers and other, net				214,913			23,589			1,336			239,838
Investments in limited partnerships				25,489			—			—			25,489
Premises and equipment				27,600			1,952			—			29,552
Capitalized software				5,783			—			—			5,783
Goodwill and other intangibles				24,331			—			56,783			81,114
Deferred taxes				9,751			3,556			(3,853	)		9,454
Other assets				7,867			3,969			3,714			15,550
Total assets			$	636,712		$	85,150		$	(45,726	)	$	676,136
Liabilities and Stockholders' Equity
Liabilities:
Accounts payable and accrued expenses			$	60,974		$	17,193		$	7,535		$	85,702
Payables to brokers, dealers and other				197,811			15,748			—			213,559
Software royalties payable				5,427			—			—			5,427
Securities sold, not yet purchased, at fair value				4,905			138			—			5,043
Income taxes payable				15,060			1,275			(3,771	)		12,564
	Total liabilities			284,177			34,354			3,764			322,295
Commitments and contingencies
Stockholders' Equity:
	Preferred stock			—			—			—			—
	Common stock			512			109			(109	)		512
	Restricted stock			—			(150	)		150			—
	Additional paid-in capital			154,877			29,044			(27,738	)		156,183
	Retained earnings			261,184			42,628			(42,628	)		261,184
	Common stock held in treasury, at cost			(64,523	)		(20,727	)		20,727			(64,523	)
	Accumulated other comprehensive income (loss):
		Currency translation adjustment		485			(108	)		108			485
	Total stockholders' equity			352,535			50,796			(49,490	)		353,841
Total liabilities and stockholders' equity			$	636,712		$	85,150		$	(45,726	)	$	676,136

See Notes to Unaudited Pro Forma Condensed Combined Financial Information

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NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

Historical Financial Information of Investment Technology Group, Inc. ("ITG") and Hoenig Group Inc. ("Hoenig")

[a]

The historical financial information of ITG as of June 30, 2002, for the year ended December 31, 2001, and for the six-month periods ended June 30, 2002 and 2001 is based upon the historical financial statements included in our filings with the Securities and Exchange Commission (the "SEC").

[b]

The historical statement of financial condition of Hoenig as of June 30, 2002 corresponds to the historical financial information included in Hoenig's filings with the SEC. The historical statements of income of Hoenig for the year ended December 31, 2001, and for the six-month periods ended June 30, 2002 and 2001, exclude the actual results of operations of Axe-Houghton Associates, Inc. ("Axe Houghton") for the respective periods as Hoenig sold its asset management subsidiary during the six months ended June 30, 2002. We adjusted the historical financial information of Hoenig to include interest income earned on the amount of cash and cash equivalents of Axe-Houghton that was paid as a dividend to Hoenig immediately prior to completion of the sale of Axe-Houghton.

The historical statements of income of Hoenig include the following gains and losses:

•

During the six-month period ended June 30, 2002, Hoenig recorded a charge of approximately $7.7 million (inclusive of legal costs) before taxes ($6.7 million after taxes) representing the loss incurred as a result of unauthorized trading in foreign securities, by a former employee of Hoenig & Company Limited, in violation of Hoenig's policies and procedures. This loss was announced by Hoenig on May 9, 2002;



•

During the six-month period ended June 30, 2001, Hoenig incurred a one-time impairment charge of approximately $9.3 million before taxes ($5.5 million after taxes) representing the entire write-off (including certain acquisition costs and accrued interest on convertible notes) of its investment in InstiPro Group, a business-to-business on-line brokerage firm, in which Hoenig had invested $7.5 million in 2000;



•

During the six-month period ended June 30, 2001 and during the twelve-month period ended December 31, 2001, Hoenig recognized pre-tax gains of $1.5 million and $1.9 million ($1.2 million and $1.4 million after taxes), respectively, relating to the sale of shares of stock that they held in the London and Hong Kong stock exchanges. These shares were received in 2000 at the time of the demutualization of these exchanges.

Excluding the above one-time gains and losses, the unaudited pro forma combined diluted earnings per share would have been $1.68 for the year ended December 31, 2001, $0.89 for the six-month period ended June 30, 2002 and $0.86 for the six-month period ended June 30, 2001.

Unaudited Pro Forma Condensed Combined Statements of Income

[c]

The historical financial information of Hoenig reflects estimated transaction costs of approximately $1.2 million incurred by Hoenig during the six months ended June 30, 2002. These costs consist primarily of fees and expenses of investment bankers, attorneys and accountants, SEC filing fees and other related charges. For the six months ended June 30, 2002, the expenses have been excluded from the pro forma combined results of operations as they are considered to be nonrecurring costs directly related to the transaction.

[d]

The historical financial information of ITG reflects the actual interest income earned on the $103.7 million cash balance paid to Hoenig stockholders on the date of acquisition. The estimated

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interest income amounts earned on such balance for the respective periods have been excluded from the pro forma combined results of operations as such amounts would not have been earned if ITG had acquired Hoenig at the beginning of each of the periods presented.

[e]

Pro forma adjustments also reflect reclassifications of certain Hoenig statement of income amounts to conform to the financial statement presentation of ITG. Independent research and other expenses previously reported as a separate expense line item in Hoenig's statement of operations were netted against the corresponding revenues. Also, certain items previously classified as other general and administrative expenses were allocated between other revenues, occupancy and equipment, and telecommunications and data processing services.

[f]

The calculation of the diluted weighted average number of common shares outstanding has been adjusted to reflect the dilutive effect of certain ITG options and awards issued in exchange for Hoenig awards that existed on September 3, 2002.

Unaudited Pro Forma Condensed Combined Statement of Financial Condition

[g]

On September 3, 2002, the purchase price of Hoenig was approximately $107.8 million, which primarily represents cash paid to Hoenig stockholders, including $10.1 million of cash paid to Hoenig employees in relation to the cash out of Hoenig stock options, which had vested and were exercisable on the date of acquisition. The Hoenig stockholders received $11.58 per share, of which $0.23 per share or $2.4 million in the aggregate, have been placed into an escrow account. In connection with this acquisition, ITG also incurred transaction costs consisting primarily of professional fees of approximately $2.8 million, which have been included in the purchase price.

The unaudited pro forma condensed combined statement of financial condition as of June 30, 2002 reflects the allocation of the purchase price, which was recorded using management's estimates and preliminary evaluation. The actual purchase price accounting adjustments to reflect the fair value of net assets will be based on management's final evaluation, therefore, the information provided in the unaudited pro forma condensed combined statement of financial condition is subject to change pending the final allocation of purchase price.

The following is a summary of the preliminary allocation of the purchase price in the Hoenig acquisition as reflected in the unaudited pro forma condensed combined statement of financial condition as of June 30, 2002 (dollars in thousands):

Purchase price	$	105,012
Acquisition costs		2,795
Total purchase price	$	107,807
Historical net assets acquired		50,796
Tax benefit on cash out of Hoenig stock options		3,771
Write-up of exchange seats and trading rights		4,200
Write-up of "Hoenig" trade name		486
Write-down of deferred tax assets		(3,659	)
Liabilities for restructuring and integration costs incurred		(3,236	)
Other, net		(848	)
Goodwill		56,297
Total purchase price	$	107,807

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QuickLinks

Exhibit 99.3

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION
NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION