Patients with chronic and severe personality disorders place heavy demands on Health and Social Services. In this paper we present the findings of a research study which evaluated the impact of specialized inpatient psychosocial treatment on patterns of Health Service utilization in patients referred for admission to the Cassel Hospital. The comparison between a pre-treatment and a post-treatment sample showed a significant decrease in the use of medical, surgical and psychiatric services in the year following discharge from the hospital. We also found that the post-treatment group relied less on the use of psychotropic medication, on cigarette and alcohol consumption, while the employment rate was increased. This paper adds to the already substantial scientific literature to show that psychotherapy and psychosocial forms of treatment make economic sense, as well as improving the psychological health of patients.