Montgomery County police have cited 18 county businesses, including two county-owned liquor stores, for selling alcohol to minors after a weekend sweep in which they were assisted by a 17-year-old youth.

One of the county-owned stores cited was the site last October of County Executive Charles W. Gilchrist's announcement of a crackdown on liquor law violators.

Police said they visited 28 bars, restaurants, liquor stores and delicatessens with a 6-foot, bearded youth who attempted to buy alcoholic beverages. During some of the visits, a policewoman dressed in a jogging suit waited in the stores to witness the illegal sale.

Except for those persons who were already 18 when the drinking age was raised last year, Maryland law sets 21 as the legal age for purchasing any alcoholic beverages.

Ten businesses where the youth tried to buy alcoholic beverages refused to sell to him. The 18 establishments that did sell alcohol to the youth face heavy fines and possible license suspensions.

The large number of citations raised questions yesterday about the effectiveness of a supposed crackdown on liquor law violators. Gilchrist had held the press conference last fall in the midst of a tough election campaign against an opponent who opposed the county's operation of liquor stores. He touted the advantages of having the county in the liquor business, saying the government could exercise greater control over enforcing the drinking laws.

"If these were county liquor stores . . . it points up the need for stronger enforcement," said Paul Daley, a member of the Montgomery County chapter of the Mothers Against Drunk Driving and a recent appointee to the county's drunk driving task force.

The county official in charge of retail operations for the Department of Liquor Control declined to comment until he saw the police report.

The citations prompted Dennis Theoharis, the county's alcoholic beverage program manager, to question if penalties should be toughened.

Theoharis said his own license inspectors, who investigate on-sale premises each weekend, had about a 6 percent rate of violation. Thirteen stores have been cited for violations since July of last year, mostly for selling alcohol to minors, he said.

Some of those cited argued that the methods police used amounted to "entrapment."

"They hit us on a Friday or Saturday night when it's real busy," said Steve Auerbach of the Potomac Village Deli, which was cited for the second time on the same offense. "And the 17-year-old had a full beard and he was 6-feet tall."