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Exhibit 12.1

Corporate Office Properties Trust

Ratio of Earnings to Combined Fixed Charges and Preferred Share Dividends

(Dollars in thousands)

			Years Ended December 31,
Earnings:			2010			2009			2008			2007			2006
Income from continuing operations before equity in income (loss) of unconsolidated entities and income taxes			$	39,016		$	60,907		$	56,728		$	30,840		$	32,532
Gain on sales of real estate, excluding discontinued operations				2,840			—			1,682			3,108			889
Combined fixed charges and preferred share dividends (from below)				135,836			115,014			122,395			127,139			111,787
Amortization of capitalized interest				1,363			1,105			890			695			527
Distributed income (loss) of equity investees				—			—			(203	)		(224	)		26
Subtract:
	Capitalized interest (from below)			(16,524	)		(15,461	)		(18,312	)		(19,964	)		(14,766	)
		Preferred share dividends included in fixed charges		(16,102	)		(16,102	)		(16,102	)		(16,068	)		(15,404	)
		Preferred unit distributions included in fixed charges		(660	)		(660	)		(660	)		(660	)		(660	)
		Issuance costs associated with redeemed preferred shares		—			—			—			—			(3,896	)
Total earnings			$	145,769		$	144,803		$	146,418		$	124,866		$	111,035
Combined fixed charges and preferred share dividends:
Interest expense on continuing operations			$	101,865		$	82,187		$	86,368		$	88,070		$	73,395
Interest expense on discontinued operations				263			233			553			1,950			3,045
Capitalized interest (internal and external)				16,524			15,461			18,312			19,964			14,766
Amortization of debt issuance costs-capitalized				19			30			32			138			237
Interest included in rental expense				403			341			368			289			384
Preferred share dividends				16,102			16,102			16,102			16,068			15,404
Preferred unit distributions				660			660			660			660			660
Issuance costs associated with redeemed preferred shares				—			—			—			—			3,896
Total combined fixed charges and preferred share dividends			$	135,836		$	115,014		$	122,395		$	127,139		$	111,787
Ratio of earnings to combined fixed charges and preferred share dividends				1.07			1.26			1.20			0.98			0.99
Deficiency												$	2,273		$	752

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Exhibit 12.1

Corporate Office Properties Trust Ratio of Earnings to Combined Fixed Charges and Preferred Share Dividends (Dollars in thousands)