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,
	2011			2010			2009			2008			2007
Earnings:
(Loss) income from continuing operations before equity in (loss) income of unconsolidated entities and income taxes	$	(123,044	)	$	35,352		$	55,703		$	54,299		$	28,218
Gain on sales of real estate, excluding discontinued operations	2,721			2,840			—			1,682			3,108
Combined fixed charges and preferred share dividends (from below)	139,159			135,836			115,014			122,395			127,139
Amortization of capitalized interest	1,610			1,363			1,105			890			695
Distributed loss of equity investees	(31		)	—			—			(203		)	(224		)
Subtract:
Capitalized interest (from below)	(17,400		)	(16,524		)	(15,461		)	(18,312		)	(19,964		)
Preferred share dividends included in fixed charges	(16,102		)	(16,102		)	(16,102		)	(16,102		)	(16,068		)
Preferred unit distributions included in fixed charges	(660		)	(660		)	(660		)	(660		)	(660		)
Total (loss) earnings	$	(13,747	)	$	142,105		$	139,599		$	143,989		$	122,244
Combined fixed charges and preferred share dividends:
Interest expense on continuing operations	$	101,281		$	98,748		$	79,789		$	82,401		$	85,076
Interest expense on discontinued operations	3,020			3,380			2,631			4,520			4,944
Capitalized interest (internal and external)	17,400			16,524			15,461			18,312			19,964
Amortization of debt issuance costs-capitalized	183			19			30			32			138
Interest included in rental expense	513			403			341			368			289
Preferred share dividends	16,102			16,102			16,102			16,102			16,068
Preferred unit distributions	660			660			660			660			660
Total combined fixed charges and preferred share dividends	$	139,159		$	135,836		$	115,014		$	122,395		$	127,139
Ratio of (loss) earnings to combined fixed charges and preferred share dividends	(0.10		)	1.05			1.21			1.18			0.96
Deficiency	$	152,906											$	4,895