SPRINGFIELD, Va. (AP) _ Nancy Reagan and Princess Diana heard gut-wrenching stories about drug abuse Monday from teen-agers striving to recover at a suburban drug treatment center.

The two attended a 40-minute ''rap session'' at a program known as Straight, where they listened intently as one young girl told how she stabbed herself in the eye with a needle to get attention and a young man explained his regret at having tried to strangle his father.

All rattled off long lists of drugs they had they said had influenced their behavior, including alcohol, marijuana, heroin, cocaine and hallucinogens. Teary-eyed parents, their voices choking with emotion, stood up to criticize or praise their children.

''There's a great big, wonderful world out there waiting for you. We need you, but we need you clear-eyed and clear-minded,'' Mrs. Reagan told the group of about 150 teens and 300 adults after the session.

''Just stay with it. I love you, all of you,'' Mrs. Reagan said, her voice catching.

The princess, her faced deeply flushed, said nothing at the end of the emotional session, but smiled as she accepted a small statue and two T-shirts from a leader of the session.

She laughed when the young man said the shirts could be used ''for the jogging you or your husband may do.''

The two women sat quietly in the front row, their backs to the television cameras. Mrs. Reagan wore a red Aldolfo coat-dress, the princess a white wool suit. They chatted now and again, and sat facing the group of youngsters, most dressed in jeans and sport shirts.

Diana appeared startled when one of the young men lept up from the group and shouted when his father called on him from across the room. The young man had received permission to rise to a higher step in the program, and the teens clapped and screamed approval as he ran across the room to hug his father and mother.

Youngsters in the program spend much of their time in such sessions as part of the program's method of using group therapy to keep the teen-agers drug free, on the theory that peer pressure got them involved in drugs.

The visit was Mrs. Reagan's third to a branch of Straight Inc., a non- profit corporation that was founded in St. Petersburg, Fla., in 1976, and has branches in Orlando., Fla., Cincinnati, Atlanta, and Detroit, as well as Springfield.

Before the session, Mrs. Reagan and the princess held a private meeting with two former members of the program, Kathy Turner, 17, and Mike Kirsch, 18, and their parents and some officials from the program.

According to those who attended the session, Mrs. Reagan smiled and nodded encouragement as the two told their stories of drug abuse. The princess questioned the two about their drug use in a low and serious tone. She said she was curious whether their drug use was ''to escape the responsibility life puts on us,'' and if the program had made them ''feel a stronger person after you leave,'' said one who attended the session.

At the end of the discussion, the princess leaned over to the director of the program, Page Peary, and said, ''If its any consolation, it's easier to ask questions,'' the observer reported.

''She seemed a little shy, but she became more confident as the meeting went on,'' Kirsch said after the session.

''I'd like to talk to her again. I would have liked to ask her out to dinner, but I didn't think that was too cool,'' he said.

Miss Turner said the princess ''seemed very intelligent, interested in learning things.'' She said she told the princess how she used to run away from home repeatedly because of her drug use.

''It was kind of hard to talk, but I'm very happy that two such important people are directing attention to the drug problem,'' she said.