Montgomery County police set up roadblocks along Connecticut Avenue north of Chevy Chase Circle last night in an attempt to find witnesses to a hit-and-run accident last Thursday in which an 8-year-old Chevy Chase boy was killed.

For 90 minutes, eight traffic squad officers halted cars entering the 7100 block of Connecticut Avenue and asked drivers if they had any knowledge of the Nov. 29 hit-and-run acident, which fatally injured Jeremy Grodsky of 7317 Maple Ave.

Jeremy, son of Dr. David and Marlene Grodsky, was crossing Connecticut Avenue with his father about 8:30 p.m. after attending a cub scout meeting at a local church, when a car described as a dark green, late model Capri with Maryland license plates struck the boy.

Dr. Grodsky, a psychiatrist, administered mouth-to-mouth resuscitation on the scene but the boy died about two hours later.

Officer Michael Pupjak, who participated in last night's roadblock, the second i n a week, said police were "looking for anyone who might have seen something in the area that night . . . we're kind of grabbing at straws."

Pupjak, who has been on the force for seven years, said this was the first roadblock of its kind he has seen in the area. "Hit-and-run fatals are rare in this area, and in the cases that we do have, usually there are witnesses who can supply more positive identification of the vehicle involved."

Pupjak said future roadblocks are planned, and that during the next week police will hypnotize witnesses who have already come forward in hopes that they can then recall the license number of the hit-and-run auto.