Objective - The aim of this study was to asses type and prevalence of Personality Disorders (PDs) and their patterns of comorbidity with Axis I disorders in a sample of psychiatric inpatients. Setting - The sample consisted of 300 subjects admitted to a psychiatric unit on a voluntary bases for an index episode. The study was conducted over a period of 12 months, from 1.11.1997 to 31.10.1998. Main outcome measures - The Italian version of SCID-II-PQ (Structured Clinical Interview for DSM-III-R personality disorders, with Personality Questionnaire-PQ- a self report questionnaire). Results - More than half the patients had at least one personality disorder. The mean of disorders per patient was 2.83±1.93 (±SD). The most prevalent Axis II disorders were Borderline PD (30.7%), Obsessive-compulsive PD (30.7%) and Avoidant PD (25.3%). Women were significantly more likely than men to meet criteria for Dependent PD and Avoidant PD. Man showed significantly more frequently than women Antisocial PD. Significant associations (p<0.05) were found for comorbidity of Mood Disorders and Avoidant PD, and for Psicoactive Use Disorders and Antisocial PD. Conclusions - Our study confirms the high prevalence of PDs in psychiatric inpatients and showes some interesting associations between Axis I and Axis II disorders. These results can't be generalized to outpatients because our clinical sample involved mainly severely ill inpatients, but they raise questions about the exact nature of PDs and of the relationship with Axis I disorders. Further research involving outpatients and general population is needed to examine factors that could affect development and course of Personality Disorders.