"Nike has dominated the best shelf space at the big-box retailers," said Peter Arnell, the chairman and chief executive at the Arnell Group in New York, an agency owned by the Omnicom Group that has worked for Reebok since 2001.

"At retail, this will provide a more efficient model" for chains to play up the products bearing the Adidas and Reebok brands, Mr. Arnell said, "so they'll have more presence and power in the stores."

Steve Stoute, who worked with Mr. Arnell on campaigns that introduced a product line for Reebok under the Rbk name, said the Reebok acquisition was "the right thing" for Adidas to do "for Nike to feel the pressure of competition" -- with a big if.

Adidas must "treat the Adidas and Reebok brands separately," said Mr. Stoute, who now works for Reebok as the chief creative officer at Translation Consulting and Brand Imaging in New York. "There's a potential problem if consumers see the lines as being blurred, so you have to treat them as standalones." Adidas executives said yesterday that the two brands would continue to have separate identities, marketing campaigns, distribution and sales forces.

The Adidas brand presents itself to consumers as a technology-focused performance product for athletes, particularly soccer players, as evidenced by its endorsement deals with stars like David Beckham, although it has some lifestyle ads that feature nonathletes like the singer Missy Elliott.

Since last year, Adidas campaigns have carried an inspirational theme, "Impossible is nothing," featuring special effects and athletes like Muhammad Ali and his daughter, Laila. Adidas ads have been produced since 2002 by a partnership between 180, an agency in Amsterdam, and the San Francisco office of TBWA/Chiat/Day, part of the TBWA Worldwide unit of Omnicom. (A TBWA/Chiat/Day predecessor, Chiat/Day, created campaigns for Nike in the 1980's and for Reebok in the early 1990's.)

The Reebok brand image contains elements of lifestyle as well as performance, focused on sports leagues with which it has licensing agreements like the National Basketball Association, the National Football League and the National Hockey League. The Rbk sub-brand is focused on life style through the deals brokered by Mr. Stoute that paired Rbk with hip-hop artists like Jay-Z and 50 Cent; Mr. Stoute and Translation signed another artist, Nelly, for Rbk.