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,
	2008			2007			2006			2005			2004
Earnings:
Income from continuing operations before equity in loss of unconsolidated entities, income taxes and minority interests	$	63,488		$	35,138		$	34,796		$	38,151		$	39,879
Gain (loss) on sales of real estate, excluding discontinued operations	1,682			3,108			889			366			(150		)
Combined fixed charges and preferred share dividends (from below)	118,491			123,387			110,541			85,240			70,627
Amortization of capitalized interest	890			695			527			337			285
Distributed income (loss) of equity investees	(203		)	(224		)	26			(164		)	(83		)
Subtract:
Capitalized interest (from below)	(17,632		)	(19,274		)	(14,559		)	(9,871		)	(5,112		)
Preferred share dividends included in fixed charges	(16,102		)	(16,068		)	(15,404		)	(14,615		)	(16,329		)
Preferred unit distributions included in fixed charges	(660		)	(660		)	(660		)	(660		)	(179		)
Issuance costs associated with redeemed preferred shares	—			—			(3,896		)	—			(1,813		)
Total earnings	$	149,954		$	126,102		$	112,260		$	98,784		$	87,125
Combined fixed charges and preferred share dividends:
Interest expense on continuing operations	$	83,646		$	85,576		$	72,984		$	55,979		$	43,663
Interest expense on discontinued operations	51			1,382			2,417			3,405			3,031
Capitalized interest (internal and external)	17,632			19,274			14,559			9,871			5,112
Amortization of debt issuance costs-capitalized	32			138			237			272			113
Interest included in rental expense	368			289			384			438			387
Preferred share dividends	16,102			16,068			15,404			14,615			16,329
Preferred unit distributions	660			660			660			660			179
Issuance costs associated with redeemed preferred shares	—			—			3,896			—			1,813
Total combined fixed charges and preferred share dividends	$	118,491		$	123,387		$	110,541		$	85,240		$	70,627
Ratio of earnings to combined fixed charges and preferred share dividends	1.27			1.02			1.02			1.16			1.23