There is an increasing interest in mentally ill offenders’ (MIOs) treatment experiences in forensic settings. This study focuses on the treatment perspectives of MIOs in treatment as well as in prison settings in Flanders. Seventeen MIOs were interviewed about the treatment they received. Data were analyzed using thematic analysis to derive key themes while acknowledging the individuality of the participants’ experiences. Treatment perspectives of MIOs in both settings revolved around similar themes, including "good" staff and privacy. However, their views differed on two themes: MIOs in treatment settings reported on feelings of lacking control and experiencing too much pressure, whereas MIOs in prison settings reported the opposite. The positive experiences in prison settings may complicate the transition from prison to a forensic treatment setting. The study further underscores the major challenge to create more opportunities for MIOs to meet their needs of self-determination in secure forensic treatment settings.