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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,
		2007			2006			2005			2004			2003
Earnings:
Income from continuing operations before equity in loss of unconsolidated entities, income taxes and minority interests		$	35,570		$	35,313		$	38,324		$	40,031		$	31,487
Gain (loss) on sales of real estate, excluding discontinued operations			3,108			889			366			(150	)		472
Combined fixed charges and preferred share dividends (from below)			123,387			110,541			85,240			70,627			71,541
Amortization of capitalized interest			695			527			337			285			254
Distributed income (loss) of equity investees			(224	)		26			(164	)		(83	)		(181	)
Subtract:
	Capitalized interest (from below)		(19,274	)		(14,559	)		(9,871	)		(5,112	)		(2,846	)
	Preferred share dividends included in fixed charges		(16,068	)		(15,404	)		(14,615	)		(16,329	)		(12,003	)
	Preferred unit distributions included in fixed charges		(660	)		(660	)		(660	)		(179	)		(1,049	)
	Repurchase of preferred units in excess of recorded book value		—			—			—			—			(11,224	)
	Issuance costs associated with redeemed preferred shares		—			(3,896	)		—			(1,813	)		—
Total earnings		$	126,534		$	112,777		$	98,957		$	87,277		$	76,451
Combined fixed charges and preferred share dividends:
Interest expense on continuing operations		$	82,032		$	70,260		$	53,906		$	41,423		$	37,905
Interest expense on discontinued operations			1,250			2,160			3,238			2,840			3,274
Capitalized interest (internal and external)			19,274			14,559			9,871			5,112			2,846
Amortization of debt issuance costs on continuing operations—expensed			3,676			2,847			2,229			2,420			2,756
Amortization of debt issuance costs on discontinued operations—expensed			—			134			11			11			11
Amortization of debt issuance costs-capitalized			138			237			272			113			—
Interest included in rental expense			289			384			438			387			473
Preferred share dividends			16,068			15,404			14,615			16,329			12,003
Preferred unit distributions			660			660			660			179			1,049
Repurchase of preferred units in excess of recorded book value			—			—			—			—			11,224
Issuance costs associated with redeemed preferred shares			—			3,896			—			1,813			—
Total combined fixed charges and preferred share dividends		$	123,387		$	110,541		$	85,240		$	70,627		$	71,541
Ratio of earnings to combined fixed charges and preferred share dividends			1.03			1.02			1.16			1.24			1.07

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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)