The prevalence of personality disorders in bipolar patients varies widely as reported in the literature. The Personality Diagnostic Questionnaire-Revised (pdq-r) is a selfreport instrument for dsm-iii-rpersonality disorders with high sensitivity and moderate specificity. This study was designed to assess personality disorders in bipolar patients (criteria dsm-iii-r) using the pdq-r. More than half of the 87 patients (47) who completed the pdq-rscored for one or more personality disorders. A total of 121 diagnoses was made among 47 patients, a mean of 2,6 per patient. The most frequent diagnoses were histrionic, borderline and paranoid personality disorder (26, 19 and 16). The results were compared with the study of O'Connell (1991). The pdq-r is a useful instrument in clinical practice. The comorbidity of personality disorders and bipolar disorder is evident. This can be important in treatment. It is advisable to conduct a semi-structured interview when a personality disorder is found, because of the possibility of overdiagnosing.