This report compares young adult admissions to admissions of youths aged 12 to 17, who accounted for 8 percent of Treatment Episode Data Set (TEDS) admissions in 2004. The report further breaks down the young adult admissions into two subgroups: those aged 18 to 21 (9 percent of all admissions); and those aged 22 to 25 (12 percent of all admissions). This report is based on the Drug and Alcohol Services Information System (DASIS), the primary source of national data on substance abuse treatment. DASIS is conducted by the Office of Applied Studies (OAS) in the Substance Abuse and Mental Health Services Administration (SAMHSA). Young adults aged 18-25 were less likely than youths aged 12-17 to be admitted with marijuana as their primary substance of abuse (27% vs. 64%). The criminal justice system was the principal source of referral to treatment for 47% of young adult admissions compared to 52% of youth admissions to substance abuse treatment. About 48% of all TEDS substance abuse treatment admissions in 2004 were in the 28 States that provided data on a psychiatric problem in addition to an alcohol or drug problem for their treatment admissions. Based on this TEDS supplemental data set, 17% of young adults had a psychiatric problem in addition to substance abuse compared with 20% of the youth admissions for substance abuse treatment. (Contains 4 endnotes, 3 figures, and 1 table.)