['This study tested the hypothesis that patients with more severe substance use disorders (SUDs) at intake respond better when treated in more structured and intensive settings (i.e. in-patient/residential versus out-patient), whereas patients with less severe SUD problems have similar outcomes regardless of treatment setting.', 'Up to 50 new patients were selected randomly from each of a random and representative sample of 50 Department of Veterans Affairs (VA) SUD treatment programs (total n = 1917 patients), and were followed-up an average of 6.7 months later (n = 1277).', 'Patients completed a brief self-report version of the Addiction Severity Index (ASI) at baseline and at follow-up.', 'In mixed-model regression analyses, baseline substance use severity predicted follow-up substance use severity and there were no main effects of treatment setting. However, interaction effects were found, such that more severe patients experienced better alcohol and drug outcomes following in-patient/residential treatment versus out-patient treatment; on the other hand, patients with lower baseline ASI drug severity had better drug outcomes following out-patient treatment than in-patient treatment. Treatment setting was unrelated to alcohol outcomes in patients with less severe ASI alcohol scores.'] Do treatment setting and baseline substance use severity interact to predict patients ' outcomes?