Fairfax County juvenile court received twice as many complaints for alcohol offenses last year as it did for drug offenses, in contrast to arrest trends among suburban Maryland teen-agers.

The disparity in complaints between Fairfax and its two Maryland neighbors reflects the greater law enforcement manpower directed at curbing alcohol use among Fairfax juveniles and the stiffer penalties Virginia law imposes on juveniles' possession of alcohol as opposed to marijuana, police and court officials agree.

Alexandria and Arlington county officials were unable to provide figures on alcohol and drug complaints brought against juveniles. But they speculated that--like Fairfax--they had more complaints of alleged juvenile alcohol violations than drug complaints.

"We have both police and state investigators bringing alcohol cases," said Michael J. Valentine, a judge in Fairfax County Juvenile and Domestic Relations Court. "You don't have that situation on the drug side."

He dismissed theories that cost plays a role in the higher number of alcohol complaints. "Most of the kids that come into my court aren't hurting for money to buy grass (marijuana) or beer," he said.

"We have seen for several years, at least in Fairfax County, a tremendous increase in drinking juveniles," added police spokesman Warren Charmichael. "We've had the drug problem too, but the drinking problem has increased markedly in the last several years. The increase in complaints reflects that."

Elmer Tippett, administrative assistant to the chief of police in Prince George's County, said Maryland's lower drinking age sometimes makes it difficult for police officers to apprehend underage teen-age drinkers, who often appear old enough to drink.

Under Virginia law, purchasers must be 21 or over to purchase hard liquor and 18 or older for beer. In Maryland, beer and wine can be purchased by those 18 and older. The Maryland General Assembly this year raised the drinking age to 21, however, effective July 1.

A total of 547 complaints alleging illegal alcohol use or possession were brought against youths under 18 in Fairfax in the fiscal year ended June 1981--more than double the 258 drug complaints filed in the county that year and five times the 74 alcohol complaints filed in Montgomery or the 90 filed in Prince George's last fiscal year.

By contrast, Montgomery had 295 and Prince George's had 123 complaints against juveniles for the alleged sale or possession of drugs. Montgomery's figure was down substantially from fiscal 1979 when former Montgomery County police chief Robert DiGrazia mounted a highly publicized crackdown on drug use at county schools that resulted in the arrests of dozens of youths.

The alcohol complaints brought against juveniles consisted primarily of being drunk in public and possession of alcohol. The figures did not include complaints of teen-agers driving while intoxicated.

The figures in all three counties reflect the number of formal complaints brought against youths by parents, police officers, probation officers and others. The complaints do not reflect the number of juvenile and drug offenses actually heard by judges, since many cases are referred for counseling and others may be dropped. Yet court officials say the figures give a fairly reliable indication of the relative popularity of alcohol and drugs among youths.

"Alcohol is more observable in people; it's more difficult to detect drug use," said Michael W. Young, commander of the major crimes division in Fairfax County. "But you do see higher alcohol use among children than marijuana in the county," he said.

Valentine said that under Virginia law juveniles ordinarily get unsupervised probation for a first marijuana offense, while a juvenile can get up to 12 months in jail for alcohol use or possession.