A substantial number of patients with substance use disorders (SUDs) are mandated to treatment by the justice system. However, little is known about their characteristics and how they fare during treatment and in the longer term compared with nonmandated, justice-system-involved patients and patients not involved in the justice system. This prospective study (n=2,095) examined differences in pretreatment characteristics, treatment perceptions and satisfaction, during-treatment changes, and 1- and 5-year outcomes among these three types of patients and tested whether differences in pretreatment characteristics or during-treatment changes could help explain posttreatment outcome similarities or differences. Mandated patients had a less severe clinical profile at treatment intake, yet this did not account for their observed similar/better outcomes, which appeared because of the similar therapeutic gains made during treatment. Treatment perceptions and satisfaction were also comparable across groups. These findings appear to support the idea that judicial mandates can provide an opportunity for offenders with SUDs to access and benefit from needed treatment.