This study assesses the impact of major mental and personality disorders on the quality of life perceived by a Belgian adult male population in a forensic hospital. METHOD.-Population included 72 male patients (mean age=41.00; S.D.=9.73) from a security hospital in Belgium. The evaluations were collected between March 2002 and June 2004.We used the World Health Organization Quality Of Life-brief (WHOQOL-brief, 22). The WHOQOL-brief was developed from the larger WHOQOL-100 data sets, forwarded from fifteen international field WHOQOL centers coordinated by the Geneva centre. The WHOQOL-brief is a generic and multidimensional self-report containing 26 items. It includes one item from each of the 24 facets of the WHOQOL-100, and two more items from the overall quality of life and general health facet. Like the WHOQOL-100, all items in the WHOQOL-brief are rated on a five-point scale. Four types of scales assess the: intensity (not at all-extremely), capacity (not at all-completely), frequency (never-always) and evaluation (very dissatisfied/very bad-very satisfied/very good). While the initial conceptual framework for the WHOQOL-100 offered six domains, WHOQOL-brief is composed of four factors: (a) physical health; (b) psychological health; (c) social relations and; (d) environment. Saloppé and Pham [Saloppé X., Pham Th. Validation du WHOQOL-bref en hôpital psychiatrique sécuritaire. A paraître dans Forensic] showed that the WHOQOL-brief fulfils the psychometric qualities to be used in the evaluation of patients interned in a forensic hospital. We used the diagnostic interview schedule screening interview (DISSI, 44) to evaluate major mental disorders and the structured clinical interview for DSM-IV axis II disorders (SCID II, 19) to evaluate personality disorders.The aim of this research was to evaluate the quality of life perceived by the forensic patients. It is essential that the instructions clearly indicate this direction so as to avoid patients evoking their quality of life in another environmental context. It is thus specified that the patient must answer the questionnaire referring to the institution's unit in which he was hospitalized at the time of the evaluation.Initially, a descriptive analysis starting from the transformed scores is presented. In order to evaluate the impact of the mental disorders and the effect of the comorbidity on the quality of life perceived by the patients, in the second phase, we performed average comparisons using Mann Whitney's U-test. The data were analysed using the statistical package for social sciences (SPSS, 52), version 11.0.The forensic inpatients revealed a mean total score of 59.76 (S.D.=13.60) out of 120 on the WHOQOL-brief. The comparisons between the WHOQOL-brief factors suggested that the participants claimed to have better physical than psychological health (W=5.76, P<0.0001), environment (W=6.68, P<0.0001) and social relations (W=6.85, P<0.0001). Major mental disorders did not influence the perceived quality of life of the patients. However, the perception of their quality of life varied significantly in the case of personality disorders. Indeed, the patients with a narcissistic personality claimed to have better global quality of life than the other patients (U=120.00, P=0.005). They claimed to have better physical health, social relations and environment than those without this disorder (U=113.50, P=0.004 and U=136, P=0.011; U=159, P=0.034). Patients with an antisocial personality presented significantly higher scores on the WHOQOL-brief than those without this disorder in the social relations and physical health domains (U=445.50, P=0.020 and U=468.50, P=0.043). The diagnostic comorbidity had no impact on the quality of life of the patients. The lack of sufficient patients in the disorders groups may have contributed to this absence of result.The results of this study encourage us to further consider personality disorders associated or not with major mental disorders. This study reinforces the idea that to apprehend the quality of life of the forensic population is a fundamental element of their treatment.