Juveniles and young adults in forensic psychiatric commitment are a small minority but their treatment is subject to particular challenges. Besides disorder and offense-relevant aspects, age-specific developmental tasks must be considered. So far, there are hardly any empirical findings on change processes in the context of detention. The present pilot study presents selected results of the treatment evaluation in the forensic department for adolescents at Viersen Psychiatric Hospital (Rhineland, Germany). A total of 15 patients were examined regarding their problem behavior, mental and social stress, the risk of further delinquent behavior patterns, treatment satisfaction and motivation and various resilience factors. For this purpose, ratings of the patients, nursing staff and therapeutic personnel were assessed and compared at regular intervals. In this respect the degree of concordance or discrepancy of the different ratings in the sense of a therapeutic matching was also examined. Additionally, the ward climate was examined. According to patients and nursing staff, participants showed a significant reduction in the risk of further delinquent behavior patterns. The latter also reported a significant reduction in emotional stress in the long-term course. From the perspective of the therapeutic personnel there were no relevant developments in these aspects. There were also no significant changes in the other parameters examined. Ratings of the ward climate showed some fluctuation over time and in some cases assessments of patients and staff differed considerably. The advantages of the treatment evaluation as an objectifying procedure for the practical work in the (adolescent) forensic psychiatric commitment are discussed.