CoStar Group Announces the Winners of the CoStar Power Broker Awards Recognizing...

CoStar Group Announces the Winners of the CoStar Power Broker Awards Recognizing
the Top Dealmakers in Commercial Real Estate

BETHESDA, Md., May 27, 2009 (GLOBE NEWSWIRE) -- CoStar Group, Inc.
(Nasdaq:CSGP), the number one provider of information/marketing services to the
commercial real estate industry, and media partner Real Estate Forum magazine,
the industry's leading news publication, are pleased to announce the winners of
the 2008 CoStar Power Broker Awards(tm), recognizing the "best of the best" in
commercial real estate brokerage.

As the largest professional research organization serving the commercial real
estate industry, CoStar is in a unique position to identify the top firms and
brokers in each market. Every year, CoStar tallies the commercial real estate
sales and lease transactions that closed during the previous year and presents
CoStar Power Broker Awards to the select few in each market who closed the
highest transaction volume in commercial property sales and leases that year.

"CoStar Group is very proud to recognize the commercial real estate brokerage
firms and individual brokers who truly excelled and achieved remarkable sales
and leasing success in 2008 despite the difficult economic circumstances," said
CoStar Group President and CEO Andrew C. Florance. "We congratulate all the
award winners on their impressive professional accomplishment."

The complete list of 2008 CoStar Power Broker Award winners listed by market can
be found at http://www.costar.com/PowerBrokers/.

Now in their seventh year, the CoStar Power Broker Awards are presented to the
top firms and individual dealmakers by market (up to 20 winners in major
markets) based on their overall transaction volume for the entire year. All
awards are based on transaction data in CoStar's commercial real estate
database, the largest, independently researched database of commercial real
estate property information available online. Information in CoStar's database
is verified and continuously updated by approximately 900 CoStar researchers,
comprising the largest commercial real estate research operation of its kind.
CoStar's U.S. database contains more than 2.6 million commercial properties, and
the total U.S. square footage or gross building area tracked and maintained by
CoStar exceeds 66 billion square feet.

In addition to receiving individually customized CoStar Power Broker award
plaques, winners will be showcased on CoStar's website, as well as in a gatefold
insert included in Real Estate Forum magazine, and announced on the daily news
and information website, www.GlobeSt.com.

About Real Estate Forum

Real Estate Forum, a publication of Incisive Media, is America's premier
commercial real estate business magazine, delivering cutting-edge real estate
editorial, strategic insights and practical information. The publication covers
a wide range of topics, including alternative investment vehicles, new financing
structures, capital flows, and innovative approaches to development and leasing
trends. Also published by Incisive Media's Real Estate Group, www.GlobeSt.com
provides up-to-the-minute news as well as enriched content and services.
Incisive Media is a leading global provider of specialized business news and
information, in print, in person and online. The company's principal markets
include financial services, legal services, commercial real estate, marketing
services and risk management. More information on Incisive Media's real estate
offerings is available at http://www.incisivemediarealestategroup.com.

About CoStar Group, Inc.

CoStar Group, Inc. (Nasdaq:CSGP) is the number one provider of
information/marketing services to commercial real estate professionals in the
United States as well as the United Kingdom. CoStar's suite of services offers
customers access via the Internet to the most comprehensive database of
commercial real estate information throughout the U.S. as well as in the United
Kingdom and France. Headquartered in Bethesda, MD, CoStar has approximately
1,300 people working for the company worldwide, including the largest
professional research organization in the industry. For more information, visit
http://www.CoStar.com.

This news release includes "forward-looking statements" including, without
limitation, statements regarding CoStar's expectations, beliefs, intentions or
strategies regarding the future. These statements are subject to many risks and
uncertainties that could cause actual results to differ materially from these
statements. More information about potential factors that could cause actual
results to differ materially from those discussed in the forward-looking
statements include, but are not limited to, those stated in CoStar's filings
from time to time with the Securities and Exchange Commission, including
CoStar's Form 10-K for the year ended December 31, 2008 and CoStar's Form 10-Q
for the quarter ended March 31, 2008, under the heading "Risk Factors." All
forward-looking statements are based on information available to CoStar on the
date hereof, and CoStar assumes no obligation to update such statements.

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CONTACT: CoStar Group, Inc.
Analysts/Investors:
Brian J. Radecki, Chief Financial Officer
(301) 664-9132
bradecki@costar.com
Media:
Timothy J. Trainor, Communications Director
(301) 280-7695
ttrainor@costar.com