Introduction: The purpose of this work is to estimate the prevalence of psychiatric cases in a sample of opiate-dependent patients treated with sublingual buprenorphine in a therapeutic community regime, and to describe their progress during the first month of treatment., Methods: An observational, longitudinal, prospective study was conducted. Of the 119 opiate-dependent patients selected, 46 agreed to start treatment with buprenorphine. For organisational reasons, the psychopathological assessment was carried out on 36 of these patients. The measurement tools used were the MINI, GHQ-28, IPDE and Assessment of the Quality of Life in Psychoactive Substance Addicts (TEQLASP)., Results: The prevalence rate of any psychiatric disorder was 78%. The prevalence of Axis I diagnoses was 69.4%. The prevalence of cases in Axis II was 58.3%, and 50% of patients had concomitant Axis I and Axis II disorders. The patients with Axis I psychiatric disorders showed a significant reduction in the mean scores of the GHQ-28 scale, and in the B (anxiety/unease), C (social dysfunction), and D (depression) subscales of the GHQ-28. The differences observed between the patients with no psychiatric disorders after one month of treatment were not significant. An improvement in the quality of life wad observed in both groups, although these changes were of a lower magnitude in the group with psychiatric disorders., Discussion: The results of this study show a very high frequency of psychiatric disorders. For this reason, psychiatric illness must be actively looked for whenever we assess a drug-dependent patient., (Copyright © 2010 SEP y SEPB. Published by Elsevier Espana. All rights reserved.)