IBM Corp. has established its first suburban service center in the Washington area at Executive III, the third of a planned six-building complex being developed by Centennial Development Corp. in Reston.

The new center will service all IBM equipment, with an emphasis on personal computers, according to a spokeswoman for Centennial. The center will employ 175 people, including some drawn from existing IBM operations and some new employes. IBM also maintains a service center in the District.

IBM leased the entire sixth floor and part of the first floor, a total of 22,000 square feet. The company plans to move into its new offices, located at 1850 Centennial Park Dr., on Jan. 10.

IBM joins Allstate Insurance Co. at Executive III, a 105,000-square-foot office building. Allstate moved its mid-Atlantic headquarters there in November. Other tenants include Piedmont Airlines, Computer Consoles Inc. and the national headquarters of the Brick Institute of America.

Other recent developments in commercial realty in the Washington metropolitan area:

*Cellular One, one of two mobile-telephone companies serving the Washington-Baltimore area, will combine its administrative office and its technical center in Greenbelt.

In January, Cellular One will move into a new 20,000-square-foot facility at 7850 Walker Drive. Its administrative office currently is located in Rockville, while the technical center is in Howard County.

The company selected Greenwell Goetz Architects of Washington to design the new headquarters.

*A local architectural firm, Metro Pace Design, and its construction affiliate, Metro Pace Construction, have completed the $1 million Mazza Gallerie Access Connection, an underground walkway that links the stores and restaurants of the Mazza Gallerie to the northern end of the Friendship Heights Metro station.

The connection's design was intended to reflect the "Art Deco motif of the Mazza Gallerie interior with its use of black-and-white tile and greenhouse-topped enclosure," according to Pace.

*Blake Real Estate announced four new leases. At 1350 New York Ave. NW, National Marketing and Data Inc. leased 1,016 square feet, and Andrew Caffey leased 3,292 square feet. At 1150 Connecticut Ave. NW, ARKLA Inc. has leased 2,601 square feet. And, at 1025 Connecticut Ave. NW, the law firm of Zwerdling, Schlossberg, Liebig and Kahn has leased 3,776 square feet.

*The Center for Innovative Technology has leased 7,513 square feet in the new Hallmark Building at Renaissance Center, the office and hotel complex near Dulles International Airport. CIT, a joint venture between industry, academia and government designed to promote Northern Virginia as a base for high-tech companies, will join other tenants in the building that include British Aerospace Inc., Presidential Airways, Arundel Communications and the engineering firm of Campbell, McQueen and Paris.