The purpose of this study was to evaluate the quality of life of heroin dependent patients before and 1 year after the start of methadone maintenance treatment. Subjects were patients (n = 102) requesting treatment in a public methadone maintenance programme in Geneva (Switzerland). This was a prospective follow-up study using a validated questionnaire (SQLP). The SQLP was well accepted by patients and staff. Validity of the questionnaire was reconfirmed in this population. Compared to previously studied populations, the quality of life of heroin dependent patients before start of treatment was poor. More than half the patients were still in treatment after 1 year and their quality of life had clearly improved, in most domains. Like many of their peers in the psychiatric field, the patients had high initial expectations. Expectations decreased significantly over time. It was found that the higher were the initial expectations, the poorer was the quality of life after 1 year. The quality of life of heroin abusers requesting treatment is mediocre, and improved considerably after 1 year of comprehensive methadone maintenance treatment. Quality of life evaluation is feasible in this population and can offer an additional evaluation of quality of substance abuse treatment.