The Arlington County Board yesterday unanimously approved plans for a $150 million mixed-use development and government center behind the existing county courthouse, after expressing confidence that a recent legal setback to its construction could be overcome.

Ending nearly five years of community discussion on the project, called Court House Plaza, the board endorsed plans for a complex that will include two 14-story office buildings, a 17-story residential building, a 17-story hotel and almost 61,000 square feet of retail and commercial space, including space for eight movie theaters.

County Board member Albert C. Eisenberg said the plan "is not a perfect project [but] is a very good one . . .a project that strives to apply the hard lessons learned from Rosslyn and Crystal City."

The approval came despite concerns from some civic groups and nearby residents that there would be insufficient parking at the complex -- particularly after other projects planned for the area are completed. The plan now contains 1,878 parking spaces. Area residents had complained about the height and bulk of the buildings, which were likened to a "barrier wall" in the neighborhood.

Deliberations on the project were "way too focused on the site without considering the impact on the immediate surroundings," said Jeffrey A. Zinn, vice president of the adjacent Courtland Civic Association area.

Unlike other massive development projects the board has considered, this complex gave the board a unique opportunity to influence development because the county owns the six acres of land affected.

The site is bordered by North Court House Road and 14th, 15th and Adams streets. It will be a joint project of the Charles E. Smith Co., developer of most of Crystal City, and the Artery Organization, a Maryland-based builder.

New government offices are to be located in an office building that will be part of the first phase of construction, scheduled to be completed in 1988.

The entire complex, Deputy County Manager Anton S. Gardner said, is not expected to be completed until the early 1990s.

But the timetables are uncertain because of a Virginia Supreme Court decision last month that barred the county from leasing a part of its land to Smith-Artery for the office-commercial component.

The residential building is to be on land that the county plans to sell to the developers, so future condominium owners will be able to get a clear title to their units.

The court said the county could lease only its unused land, and it declared the land the county wanted to lease was used as a parking lot.

Although some civic groups asked the board to defer action until the legal questions were answered, county officials said the legal issues are expected to be resolved in the year it will take for developers to prepare to break ground.

Board Chairman John G. Milliken said yesterday that he expects the county and the developers to decide on a course of action on the case within 90 days.

Options include renegotiating the financing contract and seeking enabling legislation from the Virginia General Assembly next year to lease the land.

Martin D. Walsh, the developers' attorney, was optimistic about a resolution: "There's just too much at stake not to reach an agreement."

Many of the comments from residents yesterday focused on what they said they feared would be inadequate parking.

The county's staff countered that the parking was adequate, especially considering the location of a Metro station in the heart of the project area.