Despite a tradition that young people accused of the most serious crimes are held for trial in adult courts with the understanding that the punishment will be more severe, a new Justice Department study finds that an overwhelming majority of those tried as adults receive no prison sentence.

The study, released yesterday, found that among those young people convicted of crimes in adult courts, fewer than half were sent to prison, with the majority receiving fines or probation. Of those imprisoned, two-thirds received jail sentences of less than five years. The study found that many served only a small portion of the sentence.

Joseph White, who directed the study, said that in contrast, the average term of confinement in juvenile facilities following a juvenile trial was about nine months.

"The apparent reason for transferring or waiving many juveniles to adult courts -- that they will receive stiffer sentences than in juvenile courts -- does not appear to be substantiated in this research," White said.

"The key point is that there are only a small number of juveniles who are being referred to adult courts that are actually being confined for longer periods of time than could have been accommodated in the juvenile system," he said.

While young people between ages 10 and 17 comprise only 14 percent of the population, they account for almost half of persons arrested for crimes and almost one-fourth of those arrested for violent crimes. But the study found that in many states, juveniles being diverted to the adult system have not committed serious crimes. White said that many of the juveniles transferred to adult courts had committed property crimes or been arrested for drunkenness or drugs.

The study, the first of three, made a preliminary recommendation to state court systems that those who can be handled in the juvenile court system should be spared needless contact with the adult criminal court system.

It also recommends that juveniles tried as adults and sent to prison should be kept with prisoners of their own age group.