Substitution treatment of opiate addiction with methadone is the most effective way for the treatment of heroin addiction.

The aim of this research is the evaluation of the improvement of somatic and socio-professional status of patients treated with methadone.

The study is realized in medico-psychological center in Tangier, Morocco, with a sample of 101 patients under methadone. Questionnaire based mainly on the items of 'Addiction Severity Index” (ASI) is used.

The results show that the somatic status (weight, sleep and appetite) of 49% of the patients was improved, and it was weakly improved among 27% of patients. However, this somatic status declined in 14% of patients and has been in fluctuation among 22% of patients.

The evaluation of lifestyle shows an improvement of lifestyle; an increase of 10.9% of the item 'living with family” against a decrease of 19.8% of the item 'living alone/precariousness” are registered. Moreover, an increase of 69.56% and 112.5% of 'paid intermittent activity” and 'paid continuous activity” items respectively, against a decrease of 41.7% of joblessness patients.

The preliminary results of this study present an interessant impact of substitution treatment by methadone on patients’ quality of life. However, the effectiveness of the treatment depends not only on the molecule used, but it depends strongly on diagnosis, skills and attitude of the psychotherapist and on the patient’s specific characteristics and the sociocultural context.