Attention deficit hyperactivity disorder (ADHD) is a serious mental disorder that often persists in adulthood. In a pilot study, a structured skills training group program for adult ADHD led to significant symptomatic improvements. The present study evaluated the program's effectiveness, feasibility, and patient acceptability in a multicenter setting. Seventy-two adult ADHD patients were assigned to 13 two-hour weekly sessions at 4 different therapy sites. The therapy was well tolerated and led to significant improvements of ADHD, depressive symptoms, and personal health status (p < 0.001). The factors treatment site and medication did not contribute to the overall improvement. Patients regarded the program topics "behavioral analyses," "mindfulness," and "emotion regulation" as the most helpful. In this multicenter study, the therapy program showed therapist-independent effects and seemed to be disorder-specific. This warrants the effort of organizing further controlled studies.