['Major depressive disorder (MDD) frequently co-occurs in adolescents with substance use disorders (SUDs) and attention deficit hyperactivity disorder (ADHD), but the impact of MDD on substance treatment and ADHD outcomes and implications for clinical practice are unclear.', 'Adolescents (n=303; ages 13-18) meeting DSM-IV criteria for ADHD and SUD were randomized to osmotic release methylphenidate (OROS-MPH) or placebo and 16 weeks of cognitive behavioral therapy (CBT). Adolescents with (n=38) and without (n=265) MDD were compared on baseline demographic and clinical characteristics as well as non-nicotine substance use and ADHD treatment outcomes.', 'Adolescents with MDD reported more non-nicotine substance use days at baseline and continued using more throughout treatment compared to those without MDD (p<0.0001 based on timeline followback; p<0.001 based on urine drug screens). There was no difference between adolescents with and without MDD in retention or CBT sessions attended. ADHD symptom severity (based on DSM-IV ADHD rating scale) followed a slightly different course of improvement although with no difference between groups in baseline or 16-week symptom severity or 16-week symptom reduction. There was no difference in days of substance use or ADHD symptom outcomes over time in adolescents with MDD or those without MDD treated with OROS-MPH or placebo. Depressed adolescents were more often female, older, and not court ordered.'] Do major depression and treatment response in adolescents with ADHD and substance use disorder?