This study addressed the following questions for patients after 1 year of methadone maintenance treatment (MMT); (1) What are the demographic features and past history of drug use of benzodiazepine (BZD) abusers? (2) Do BZD abusers abuse more heroin, cocaine and/or cannabis and do they receive a higher methadone dosage level? (3) Do BZD abusers suffer more from hepatitis C (HCV) and do they have more HIV/HCV risk‐taking behaviors than non‐abusers? (4) Do BZD abusers have more psychopathology and more emotional distress than non‐abusers? All 148 patients who completed 1 year of MMT underwent random and twice‐weekly observed urine analysis for various drugs of abuse, responded to self‐report questionnaires (SCL‐90‐R; POMS; HIV/HCV risk‐taking behaviors), interviews (ASI) and underwent testing for hepatitis C. Abuse in this study is defined as any use during the 12th month of treatment. After 1 year of MMT, more BZD abusers ( n = 63) were single, had spent time in prison, were unemployed and had at least one parent with an addiction problem or mental illness in comparison to non‐abusers ( n = 85). They had started using heroin and cocaine earlier and currently abused more cocaine, heroin and cannabis. They had significantly more psychopathology and negative mood. They had significantly more HCV and reported more HIV/HCV risk‐taking behavior. We suggest that this group of patients is in need of more intensive pharmacological and psychological treatment.