A forensic addiction treatment order according to sec. 64 of the German Criminal Code (StGB) depends on a sufficiently concrete prospect of treatment success. The success of treatment is primarily defined as the legal probation after release. Despite the demand for a decidedly positive treatment prognosis and other prerequisites for admission, the number of forensic addiction treatment orders continues to rise. Despite an increasing empirical research interest in recent years, it has only been possible to identify useful predictors for the prognosis of treatment success to a limited extent. This is mainly due to the methodological limitations with which empirical studies in the forensic psychiatric context are always confronted, but also to the special features of the mostly investigated success criteria: Type of discharge as well as legal probation and drug use after discharge. This methodologically oriented article takes a (self-)critical look at previous research approaches and results, and outlines the prospective investigation of the development of repeated risk assessment as an alternative approach to determining predictors relevant to treatment.