EXHIBIT 21.1
 PRIME GROUP REALTY TRUST
 SUBSIDIARIES OF THE REGISTRANT
 DECEMBER 31, 2009
  Entity
    
    Property77 West Wacker Limited Partnership (3), (4)
    
    Sole member of 330 N. Wabash Avenue
Mezzanine, L.L.C. and 99.5% owner of Brush
Hill Office Center, L.L.C.180 N. LaSalle Holdings, L.L.C. (1), (3)
    
    Sole member of 180 N. LaSalle II, L.L.C.180 N. LaSalle II, L.L.C. (1), (3)
    
    180 N. LaSalle280 Shuman Blvd., L.L.C. (1), (3)
    
    280 Shuman Blvd. (Atrium)330 N. Wabash Avenue, L.L.C. (1), (3)
    
    330 N. Wabash Avenue330 N. Wabash Mezzanine, L.L.C. (1), (3)
    
    Sole member of 330 N. Wabash Avenue, L.L.C.330 Redevelopment LLC (1)
    
    Performs certain work at 330 N. Wabash Avenue800 Jorie Blvd., L.L.C. (1), (3)
    
    Former owner of 800-810 Jorie Blvd.800 Jorie Blvd. Mezzanine, L.L.C. (1), (3)
    
    Former member owning 49.0% of 800 Jorie
Blvd., L.L.C. (50.5% is owned by Prime
Group Realty, L.P.)1051 N. Kirk Road, L.L.C. (1), (3)
    
    Former owner of 1051 N. Kirk Road1600 167th Street, L.L.C. (1), (3)
    
    Former owner of 1600-1700 167th Street
(Narco River Business Center)2305 Enterprise Drive, L.L.C. (1), (3)
    
    2305 Enterprise Drive4343 Commerce Court, L.L.C. (1), (3)
    
    4343 Commerce Court (The Olympian Office Center)7100 Madison, L.L.C. (1)
    
    7100 Madison AvenueBrush Hill Office Center, L.L.C. (1), (3)
    
    Brush Hill Office CenterContinental Towers, L.L.C.
    
    Owner of Tower I, Tower III and the
Commercium at 1701 Golf RoadContinental Towers Associates II, LLC
    
    Sole member of Continental Towers
Associates III, LLCContinental Towers Associates III, LLC
    
    Owner of Tower II at 1701 Golf RoadCTA General Partner, LLC
    
    Sole member of Continental Towers, L.L.C.CTA Member, Inc.
    
    Sole member of CTA General Partner, LLCDearborn Center, L.L.C. (1), (5)
    
    Former owner of Citadel CenterLaSalle-Adams, L.L.C. (1), (3)
    
    Former owner of 208 South LaSalle StreetPGR Finance II, Inc. (6)
    
    Former member owning 1% of LaSalle-Adams,
L.L.C.PGR Finance IV, Inc. (6)
    
    Former member owning 0.1% of 1600
167th Street., L.L.C.PGR Finance VIII, Inc. (6)
    
    Limited Partner owning 0.5% of 77 West
Wacker Limited Partnership




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Entity
    
    PropertyPGR Finance XIV, Inc. (6)
    
    Member owning 0.1% in both 1051 N. Kirk
Road, L.L.C. and 4343 Commerce Court, L.L.C.PGR Finance XV, L.L.C. (1), (3)
    
    Member owning 0.5% of Brush Hill Office Center, L.L.C.PGR Finance XVII, Inc. (6)
    
    Former member owning 0.5% of 800 Jorie Blvd., L.L.C.PGR Finance XXI, L.L.C. (1)
    
    Member owning 0.1% of 2305 Enterprise Drive, L.L.C.PGR Finance XXII, Inc. (6)
    
    Member owning 1% of 180 N. LaSalle Holdings, L.L.C.PGRLP77 Manager LLC (1)
    
    Former manager of 77 W. Wacker DrivePGRLP131 Manager LLC (1)
    
    Manager of Citadel Center, 131 S. Dearborn St.PGRS 1407 BWAY LLC (1)
    
    Asset and Development Manager of 1407 Broadway Avenue, New York, NYPGRT Equity LLC (1)
    
    Owner of (i) junior loans encumbering
Continental Towers, (ii) 50% common
interest in 77 West Wacker Drive,
L.L.C., (iii) 280 Shuman Blvd., L.L.C.,
(iv) 800 Jorie Blvd. Mezzanine, L.L.C.,
and (v) Prime Group Management, L.L.C.PGRT Equity II LLC (1)
    
    Member owning 99.0% of 180 N. LaSalle
Holdings, L.L.C.PGRT ESH, Inc. (6)
    
    Former owner of interest in BHAC Capital
IV, LLCPGT Construction Co. (6)
    
    Subsidiary of Services Company for
construction workPhoenix Office, L.L.C. (1)
    
    Owner of 23.1% interest in
Plumcor/Thistle, L.L.C., owner of a
building in Thistle Landing in Phoenix,
ArizonaPrime Group Management, L.L.C. (1), (3)
    
    Manager of Continental TowersPrime Group Realty Services, Inc. (7)
    
    The Services Company, owner of 100% of
PGT Construction Co., PRS Corporate Real
Estate Services, Inc., Prime Services
Holdings, Inc. and 99.9% of 77 Fitness
Center, L.P.Prime Rolling Meadows, L.L.C. (1)
    
    Property adjacent to Continental TowersPGRT Realty Services, Inc. (6)
    
    Brokerage subsidiary of Services
Company, formerly known as PRS Corporate
Real Estate Services, Inc.
 (1)
    
    Delaware Limited liability Company(2)
    
    PGRT Equity LLC, a subsidiary of the Operating Partnership, owns a 50% common interest, PGRLP
77 Manager LLC, a subsidiary of the Operating Partnership, manages the property and a third
party owns the remaining 50% common interest.(3)
    
    We own both direct and indirect ownership interest in these entities through wholly owned
subsidiaries listed above.(4)
    
    Illinois Limited Partnership.(5)
    
    PGRT Equity LLC, a subsidiary of the Operating Partnership owns a 30% subordinated common
interest, the Operating Partnership manages the property and a third party owns the remaining
70% common interest.(6)
    
    Delaware Corporation.(7)
    
    Maryland Corporation.