Police here say a novel radio call-in show designed to get citizens to tip them to illicit drug activity has generated wide public participation, but the number of on-the-spot arrests credited to police during the four-hour show was exaggerated.

Baltimore police spokesman Dennis Hill said most of the 95 arrests credited by local news media were made by undercover officers in cases unrelated to the call-in tips.

"The bulk of the arrests were made by detectives who had already been working the street and were making other drug observations," Hill said.

Initial news reports of almost 100 on-the-spot arrests, however, were widely circulated, triggering inquiries from numerous police departments across the country and drawing praise from First Lady Nancy Reagan, a longtime advocate of programs to curb drug abuse.

Hill said he repeatedly told local reporters during the radio show that most of the arrests resulted from ongoing investigations and not the call-in tips.

"I swear I didn't hear him say anything like that," said Milford Prewitt, a Baltimore Sun reporter who covered the event.

Hill said, "Our purpose was not to get a lot of arrests that night. Our purpose was to get people motivated . . . to call in with information for follow-up investigations. In that sense, the program was a great success."

He said few of the tips resulted in instant arrests because usually "you can't make a case right on the spot . . . it requires an investigation. Sometimes it can take days . . . or months."

He said the unusually large number of arrests occurred because police deployed a specially reinforced 80-member narcotics task force to coincide with the call-in show.

Hill, who participated in the show, periodically kept listeners up to date on the number of arrests during the evening, using the numbers to boost interest in the antidrug campaign, he said.

Most of the arrests, he acknowledged, were at the "lowest level--you know, a single joint of marijuana , a single bag of heroin . Street-level stuff."

The "report-a-pusher" program -- a brainchild of Hill's and apparently the only one of its sort ever tried by a major police department in the United States -- ran from 8 p.m. to midnight on Nov. 4 during two regularly scheduled call-in talk shows on radio station WBAL.

Police set up a command post at the studio with four narcotics detectives taking calls from listeners with tips on alleged drug activity. The calls were confidential and were not put on the air. If there was a tip about on-going activity, the detectives could dispatch investigators immediately to the scene.

Meanwhile, Hill and police narcotics unit commander Lt. Joseph Newman were on the air, discussing crime and drug abuse with the talk show hosts and fielding calls from the public.

Hill said the response from tipsters was "far greater than we expected, not only in quantity but in quality."

The studio received 280 calls during the show, 231 of them "meriting investigation," according to Hill. The remaining 49 were crank calls or provided insufficient information, he said.

"The quality of information was excellent," he said. "They were giving us names of the dealers, the kind of cars they were driving, tag numbers, the stuff they were dealing."

The callers, he said, were "family people, substantial businessmen, people concerned about drugs in their neighborhoods -- not kids and young people turning each other in."

He said police are pleased with the large number of "quality tips" they got -- and are continuing to get -- as a result of the show, and expect arrests to result in coming weeks. One man was arrested 24 hours after the radio show, he said, with 12 bags of heroin worth $600 on the street.

Hill said Baltimore police are not likely to repeat the radio call-in show, "but we're looking at other ideas."

D.C. police said they were not interested in copying the Baltimore program.

"I guess it was a good publicity-type gimmick," said D.C. police spokesman Hiram Brewton. " . . . But what good is there in locking up 100 junkies a night? . . . You need to spend your time and resources getting the higher-level operators, not the junkies."