The predictive value of personality disorder (PD) on treatment length of offenders detained in high security psychiatric hospitals in the Netherlands was studied on 536 male patients (mean age 34.0 years, SD D 10.5, range: 18.0-68.8) with a 76.5% PD prevalence. Results showed that PD did not independently predict length of enforced treatment. A subgroup of patients with only PD and no comorbid major mental disorder had a shorter treatment length. This study has isolated separate factors that can shorten or prolong treatment and can provide a focus for both policy and (clinical) decision makers in the enforced treatment process.