Nearly everyone who sees economist Richard I. Cohen's resume is impressed. They write back to tell him so. But they don't offer him a job.

At 29, Cohen holds an economics degree from MIT and a master's from Princeton's Woodrow Wilson School of Public Administration. He comes to the employment market after almost six years at the Urban Mass Transportation Administration where he specialized in energy conservation planning and helped create a strategy to revitalize depressed areas through transportation. He also is familiar with contract management, policy analysis and some computer programming.

But Cohen, RIFfed from the federal UMTA and looking for work here since February, can't find a job. After sending out 175 applications and getting one fruitless interview, he now plans to enroll in graduate school to get a third degree in a more marketable field--computer sciences.

"I've been doing everything I possibly can to find a job. I've about given up," says Cohen, who wrote area firms, federal employers, Princeton alumni and state and local officials during his job quest. Last week he marched the corridors of Capitol Hill, doggedly distributing his resume to a chorus of "no openings."

These are tough times for white-collar professionals. Cutbacks in government spending and jobs, coupled with slowdowns in private industry, have hit this federal town hard. Washington, long a white-collar magnet, is no longer recessionproof, and neither are the professionals who work here.

Consultants, teachers, social workers, biochemists, reporters, office managers, sales clerks, clerical workers and even some engineers and lawyers are joining the unemployment lines these days--and staying there longer. It is not unusual, employment experts say, for a job seeker to be out of work nearly a week for every $1,000 normally earned annually.

"We're seeing a lot more people, and for the first time in my career I'm seeing people who are doing everything right and still not getting jobs," says Barbara Fitzgerald-McClain, assistant director of student and alumni career services at George Washington University. "It's an unusually tight market."

It is difficult to gauge the severity of white-collar unemployment here because accurate statistics lag behind the current problem. The Labor Department said yesterday that the nationwide jobless rate for white-collar workers was 4.9 percent, or 2.7 million people, in April. That is up from 4.0 percent, or 2.1 million, in April of last year. White-collar workers now make up roughly a fifth of the country's 10.3 million unemployed.

But the local picture is less precise, Labor Department officials say, because detailed statistics on what is happening now won't be known until 1983. An estimated 38,000 of Washington's white-collar workers were unemployed in 1981, and there is general agreement among District, Maryland and Virginia employment officials that they are seeing more out-of-work professionals today than a year ago.

An official at the D.C. Department of Employment Services, for example, says that so far this year nearly 17 percent of those applying for jobs are professional, technical or managerial workers; a year ago, the figure was 15.5 percent.

There are still jobs to be found here, although employment officials say those with technical skills fare better than social science generalists. But the pool of jobless mid-level white-collar workers is large and competition fierce.

Metro riders were only semistartled one recent morning when a tenacious job-seeker showed up at the Rosslyn subway station and peppered commuters with his resume. And more people are taking interim or entry-level work just to make ends meet, thus further tightening the job market for those just starting their careers.

Being out of work is a difficult and frightening experience for these professionals, particularly since, for many, it is the first time.

"I've never been out of a job before," says Nick Tombillo, 35, a consultant laid off in October. He holds one master's in industrial relations and another in political science and public administration, yet says he can't even find part-time work at department stores.

"Woodies wouldn't even take my application, and Sears wasn't hiring," he reports incredulously. He's sent nearly 200 resumes to area employers, both private and federal, but wherever he goes, it seems like hundreds of other hopefuls have been there ahead of him.

"I've convinced myself I'm not alone--I know I'm not alone," says Tombillo, who has recently turned to the Washington Regional Employment Services Team (WREST), a volunteer, self-help organization in Arlington for unemployed and underemployed professionals.

"I try to get up every morning as if I'm going to work," Tombillo says. "I get dressed and keep to a regular schedule." His volunteer time at WREST gives him the psychological boost to keep going; his wife's job eases the financial strain but also restricts his search to the Washington area. If he doesn't find something soon, he says he'll have to move.

Since the Washington housing market is also depressed, job-hunters often lack the mobility that is seen as crucial to any search. Still other job-seekers are being turned away by nervous employers who dub them "overqualified."

Constance Grant, a psychiatric nurse with a doctor of science degree, is job-hunting with 25 years experience in the fields of aging, public health and mental health. She managed several health-related programs and worked as a university dean, an educator and a therapist before an automobile accident interrupted her career for a year. She returned to the work force full time in 1980, taking a temporary job with the White House Conference on Aging that ended last May.

Since then, she says she has pored over newspapers ads and mailed her high-powered resume to "hundreds" of employers, a lot of whom haven't even bothered to write back. She's applied for part-time and full-time work and was told at one of the few interviews she got that she was overqualified for a position as a hospital nursing administrator.

Grant, who is in her 40s, would prefer to work full-time as a therapist and has started a small practice. But she finds the economy hasn't been any easier on her clients than on her.

"I've got to supplement my practice with an income I can count on," says Grant. "Many of my patients are looking for work themselves."

Even some lawyers here are hurting. One lawyer, RIFfed from his government job last year and still looking for a new one in the private sector, laments that he must job-hunt in a town where associates are being laid off and partners are taking pay cuts of 30 or 40 percent in several cases. Another lawyer is struggling because her clients are $25,000 behind in payments.

C. Foster Knight, an environmental lawyer, lost his job along with other lawyers at the Council on Environmental Quality soon after President Reagan took office. He very much wanted to stay in Washington and spent months looking for another position in his field here, even sticking with a consultant's job he hated so he could afford to continue his search. He finally took a job with a computer equipment company in Boston.

"Sometimes a month would go by without any bites, or else there would be 200 to 300 resumes for one decent opening," said Knight, 41. "By last summer it was looking pretty grim."

Another lawyer, Rick Colbert, 30, is so determined to work in Washington that he has taken a volunteer job on the Hill, hoping to land permanent employment there. He does part-time paid legal work on the side and lives frugally.

For a time, he says, he couldn't even give his services away; other Hill volunteers were ahead of him. He still finds job-hunting "difficult on your psyche. You can only do it so long, and then the disappointment becomes too much. You go through periods of self-doubt, feeling you're not as good as you know yourself to be."

Colbert, worrying that lawyering is no longer a growth industry, is also going to school at night to get a master's in economics.

But while lawyer Colbert is polishing up his economic skills, economist Cohen has moved into a cheaper apartment and is living off his government severance and unemployment checks. A Baltimore native, he hopes a degree in computer sciences will enable him to stay in the area.

"I want a job where I will be wanted and where other employers will be interested in hiring me," said Cohen. "This job-hunting can be very frustrating."