Arnevik WA, Pedersen G, Walderhaug E, et al. - In four different samples—(a) 136 patients in the detoxification phase, (b) 187 patients with substance use disorder in long-term inpatient treatment, (c) 1,399 patients with personality disorder (PD) in day and outpatient treatment, and (d) a community population of 935 respondents—the levels and scale reliability of (mal)adaptive personality functioning were compared and the possible clinical implications were discussed. For assessing personality pathology in substance use disorder treatment, Severity Indices of Personality Problems (SIPP) questionnaire was identified as a promising tool. Both substance use disorder samples had acceptable scale reliability for most of the self-report SIPP facets. SIPP scores in the substance use disorder samples reflected greater personality dysfunction compared with the general community population and at a level similar to the PD population. This highlights the challenges encountered in the clinical management of the substance use disorder patient group and supports the development of integrated treatment approaches.