Consolidated Statements of Operations (USD $) In Thousands, except Per Share data	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Revenues
Rental revenue	$ 99,068		$ 90,264		$ 293,547		$ 266,334
Tenant recoveries and other real estate operations revenue	22,825		20,810		65,395		59,337
Construction contract and other service revenues	18,729		13,608		67,854		77,038
Total revenues	140,622		124,682		426,796		402,709
Expenses
Property operating expenses	47,655		43,013		141,287		128,331
Depreciation and amortization associated with real estate operations	35,719		29,503		97,720		84,368
Construction contract and other service expenses	18,171		13,347		65,698		75,148
Impairment losses					57,824
General and administrative expenses	6,154		6,079		19,251		17,905
Business development expenses	1,050		2,886		2,126		3,506
Total operating expenses	108,749		94,828		383,906		309,258
Operating income	31,873		29,854		42,890		93,451
Interest expense	(25,381)		(26,174)		(78,412)		(74,042)
Interest and other (loss) income	(242)		395		3,682		1,942
Loss on early extinguishment of debt	(1,655)				(1,680)
Income (loss) from continuing operations before equity in (loss) income of unconsolidated entities and income taxes	4,595		4,075		(33,520)		21,351
Equity in (loss) income of unconsolidated entities	(159)		648		(223)		371
Income tax benefit (expense)	457		(27)		6,043		(75)
Income (loss) from continuing operations	4,893		4,696		(27,700)		21,647
Discontinued operations	2,577		1,753		(12,120)		4,276
Income (loss) before gain on sales of real estate	7,470		6,449		(39,820)		25,923
Gain on sales of real estate, net of income taxes			2,477		2,717		2,829
Net income (loss)	7,470		8,926		(37,103)		28,752
Net (income) loss attributable to noncontrolling interests:
Common units in the Operating Partnership	(178)		(363)		3,188		(1,254)
Preferred units in the Operating Partnership	(165)		(165)		(495)		(495)
Other consolidated entities	(561)		434		(1,038)		233
Net income (loss) attributable to Corporate Office Properties Trust	6,566		8,832		(35,448)		27,236
Preferred share dividends	(4,025)		(4,025)		(12,076)		(12,076)
Net income (loss) attributable to Corporate Office Properties Trust common shareholders	2,541		4,807		(47,524)		15,160
Net income (loss) attributable to Corporate Office Properties Trust:
Income (loss) from continuing operations	4,138		7,206		(24,106)		23,284
Discontinued operations, net	2,428		1,626		(11,342)		3,952
Net income (loss) attributable to Corporate Office Properties Trust	$ 6,566		$ 8,832		$ (35,448)		$ 27,236
Basic earnings per common share
Income (loss) from continuing operations (in dollars per share)			$ 0.05	[1]	$ (0.54)	[1]	$ 0.18	[1]
Discontinued operations (in dollars per share)	$ 0.03	[1]	$ 0.03	[1]	$ (0.16)	[1]	$ 0.07	[1]
Net income (loss) attributable to COPT common shareholders (in dollars per share)	$ 0.03	[1]	$ 0.08	[1]	$ (0.70)	[1]	$ 0.25	[1]
Diluted earnings per common share
Income (loss) from continuing operations (in dollars per share)			$ 0.05	[1]	$ (0.54)	[1]	$ 0.17	[1]
Discontinued operations (in dollars per share)	$ 0.03	[1]	$ 0.03	[1]	$ (0.16)	[1]	$ 0.07	[1]
Net income (loss) attributable to COPT common shareholders (in dollars per share)	$ 0.03	[1]	$ 0.08	[1]	$ (0.70)	[1]	$ 0.24	[1]

[1] Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.