BACKGROUND: Psychosocial care as an adjunct to methadone maintenance treatment is often practiced despite the low level of standardisation. AIM: The objective of this study is to determine whether group psychoeducation plus individual counselling as part of the German heroin trial is feasible and effective. METHODS: In a randomised controlled trial (he-roin vs. methadone), 513 patients received group psychoeducation plus individual counselling. RESULTS: In total, 76.8% initiated this psychosocial treatment (heroin group: 57.6%, methadone group: 42.4%). The treatment retention in both groups (heroin vs. methadone) was comparable. Patients with poor mental health condition revealed a better participation in the group psychoeducation, which was associated with a better outcome. DISCUSSION: We therefore conclude that even severely opioid dependent patients could be motivated to participate in group psychoeducation. Patients with poor mental health benefit more from psychoeducation in combination with drug counselling as from drug counselling alone.