Study results, albeit preliminary, suggest an association between depressive symptoms prior to treatment with poorer substance-use outcomes after treatment. This highlights the need for interventions that target co-occurring depressive symptoms in substance-abusing adolescents. More than half of the adolescent participants scored high on depressive symptoms as measured by the Beck Depression Inventory (BDI). A high BDI score was the only risk factor consistently associated with poorer treatment outcomes across both the 3-month, 6-month, 9-month, and 12-month followup period as a whole and at the 12-month assessment. This shows the predictive utility of the BDI. These findings also show the central importance and impact of emotional states on adolescent substance abuse. A limitation of this study is that both depression symptoms and substance use outcomes were obtained by self-reports, with no validation from collateral sources. Study participants were 153 adolescents who entered a residential treatment program (mean age of 16.6 years and 78 percent male). The study was conducted at Mountain Manor Treatment Center (MMTC), a substance abuse treatment program for adolescents. The components of substance treatment included 12-step induction, relapse prevention, refusal skills, and prosocial activities training. In addition, patients are referred based on clinical needs for psychiatric evaluation and treatment. Data were obtained from MMTC patients enrolled in the Adolescent Treatment Models study, a multisite longitudinal evaluation. 2 tables and 46 references