Dozens of Fairfax County adolescents are not receiving adequate treatment for drug abuse because of long waiting lists and prohibitive costs at residential centers, according to members of an advisory committee appointed by the Board of Supervisors.

"From the statistics we've seen, there is a very large unmet need," said Stephen Hershkowitz, chairman of the Alcohol and Drug Steering Committee, a panel named by the supervisors last fall to study the problem of adolescent drug and alcohol abuse.

In addition to the lack of adequate residential treatment, the committee has been told that outpatient clinics are overloaded and that prevention programs are scarce.

The committee has no statistics on adolescent drug use in the county -- it plans to conduct a survey -- but officials say Fairfax probably is comparable to Montgomery County, where a recent school system survey found that 73 percent of students have tried alcohol and 13 percent have tried marijuana. Smaller percentages admitted to using harder drugs. Officials say drug use is down substantially but caution that results of drug use surveys must be viewed with skepticism.

Fairfax school officials' statistics on discipline cases show that suspensions on drug charges have declined during the past five years from 1,000 a year to fewer than 500. There are 131,000 students in the Fairfax public school system.

The county runs three types of treatment programs for adolescents, all jammed to capacity. There are six outpatient treatment centers where adolescents can spend three or four afternoons a week in treatment while attending their neighborhood schools. A more intense day program is offered for eight teen-agers who attend a special school and receive treatment while living at home, and Crossroads, a residential center, has 10 places for adolescents who need long-term therapy lasting an average of nine months.

Treatment includes group therapy sessions, drug education and sports and other teamwork activities.

The 10 residential beds at Crossroads are always occupied, and the waiting list is limited to 10 because the wait for treatment can be lengthy, said Joan Volpe, director of alcohol and drug programs for the Fairfax-Falls Church Community Services Board, which serves Fairfax County and the city of Falls Church.

County School Board Chairman Mary E. Collier, a member of the committee, noted that outpatient clinics have been affected by the demand for residential programs.

Until July, when county officials ordered that all adolescent cases be handled within 72 hours, waits for outpatient care could be as long as three weeks.

Those with money or health insurance coverage can enroll in private residential programs, but some travel as far as Charlottesville to find an available bed.

Insurance coverage for drug abuse often runs out after a month, however, and many parents cannot afford to pay the costs of the programs, which range from $5,000 to $15,000 a month, officials said.

Last year, 80 of the 286 county youths who checked into private residential treatment facilities had to leave after 28 days -- even though they were not ready to do so -- because their insurance ran out, Volpe said.

One gap in county services, she said, is the lack of a 30- to 90-day residential program.

Collier recently urged her fellow panelists to recommend construction of two county-run residential treatment centers to house 30 young patients.

Supervisor Nancy K. Falck (R-Dranesville), who appointed Collier to the School Board, said supervisors would be sympathetic to such a request.

Collier said she is frustrated by the committee's lack of action, especially because the supervisors will begin developing next year's budget in the fall.

"We've been together for some time now, and I thought I would identify from the school system's point of view what those needed services are," she said.

The committee was to issue its report in July but has pushed off its final report until next year.

Hershkowitz blames the delay on problems gathering accurate information and freeing county staff from day-to-day emergencies to work on the study.

The 19-member committee includes representatives of virtually every county group and agency that deals with drug abusers, including the School Board, law enforcement offices and courts, the Chamber of Commerce, Fairfax Hospital system and county medical society.

It is to recommend improvements to the supervisors after the study is completed.

The supervisors ordered the study shortly after the White House declared a new war on drugs and a few months after the cocaine-induced death of University of Maryland basketball star Len Bias last year.

When officials interviewed patients at county clinics, Volpe said, some said they began experimenting regularly with marijuana and alcohol between the ages of 9 and 12, and a few said they started as early as 5. Some stop after a brief fling. Others move on to cocaine, PCP, LSD and inhalants, becoming serious abusers by their early teens.

Some committee members say they also are concerned about the lack of programs to catch adolescents before they get into serious trouble with drugs. One effort to do that, set up at the committee's instigation, has had mixed success. The program, Say'N No, offers low-key counseling to teen-agers and family members concerned about drug use but not ready to admit that they need treatment.

Only 30 teen-agers and 85 family members have called the town house on Franconia Road, where the program is located, since it began operations in April. But Volpe predicted the number would grow as young people learn to trust the program, which promises confidentiality. "It's going to take a little bit of time," she said.