Personality disorder characteristics can be a complicating factor among people with intellectual disabilities (ID). Persons exhibiting such features are associated with risk for violence and service instability. The purpose of this paper was to study an evaluative tool for personality disorders in people with ID and mental health disorders in community-based services. A new staff-rated instrument, the Personality Disorder Characteristics Checklist (PDCC; Taylor & Novaco, 2013) [1], was used. This tool is designed to screen for ICD-10 dissocial and emotionally unstable personality traits. In the study, the instrument was assessed for both its reliability and validity. Fifty-two randomly selected patients with ID in the specialist habilitation services in Norway were scored on the PDSS. The male/female proportion was 30/22 and the mean age was 36.8 (SD = 13.4). The internal consistency of the PDCC was found to be very good. Supportive evidence for concurrent and discriminant validity was obtained in conjunction with other relevant staff-rated instruments. There were twenty-three patients who screened above cut-off for the diagnostic criteria of a personality disorder and two patients previously diagnosed with personality disorder. This demonstrates that such disorders are present in people with ID. It also suggests that such characteristics may have been neglected in the past in providing services to this population.