THE BASIC PREMISE of regional cooperation - that what one jurisdiction does affects another - is finally being applied to efforts to attract new businesses and jobs to the separate jurisdictions of the Washington area. Local governments are coming to realize that changes in living and work habits call for new thinking in promoting economic development.

It's not that competition between the jurisdictions for new business is bad. But once, say, Prince George's County attracts a new firm, where will the employees come from? As Metro's rail system spreads, District residents may well get those jobs.

With unemployment among black youths in the city running above 40 percent, the possibility of new jobs in the suburbs is good news for the city. But to turn it around, that rate of joblessness is a danger signal to the entire area's economy and a threat to the tax bases of all the local governments.

A leader in promoting regional cooperation in economic development is Arrington Dixon, the District councilman who is the current chairman of the Metropolitan Washington Council of Governments. "We are hurting our own local programs by a simple case of not talking to each other," he notes, pointing out that there are nearly 40 firms doing business in more than one location in this region and that they employ 140,000 people.

In terms of hiring, in fact, jurisdictional boundaries mean less and less. More than 100,000 blacks in the area got jobs in the suburbs from 1970 through 1977, according to a survey by Brimmer & Company, economic consultants. But while District residents earned 44.6 percent of all the wages and salaries paid to people who worked in the city in 1970, by the end of 1977 that figure had dropped to 39 percent. These figures suggest that the city must be concerned about employment opportunities for its residents on both sides of the District line.

So far, the suburban leaders have been supporting Mr. Dixon's efforts. As Fairfax County Supervisor Martha Pennino has said, "What is a problem for the District of Columbia is a problem for the region." To that, we add that what is an unemployement problem in one part of the region can be a property-tax problem in another.

The Metropolitan Washington Board of Trade, recognizing this interdependence, has been trying to attract new businesses to the entire region. In turn, the Council of Governments is working on an economic development policy for the region, with an emphasis on training and jobs for the older urban and suburban communities. The idea makes sense and deserves the continued support of every local government in greater Washington.