Sixty-six patients satisfying the criteria for seasonal affective disorder (SAD) winter depression type (n = 57) or subsyndromal SAD (n = 9), were interviewed in a nondepressed state with the Structured Interview for DSM-III-R Personality Disorders (SIDP-R). Twenty-three percent of the patients in the SAD sample met DSM-III-R criteria for one or more categorical diagnosis of personality disorder (PD). Disorders in cluster C occurred in 18% of the sample, while 12% had cluster B PDs and 5% a cluster A disorder. The relative number of positive criteria, as a dimensional measure of PD, were higher for all cluster C disorders than for any PD in the other clusters. Our data indicate that the pattern of personality disorders in patients with winter SAD are similar to that previously reported for outpatients with non-SAD major depression. We explored the relationship between lifetime severity and clinical manifestation of SAD and dimensional measures of PD with multiple regression analyses. No significant association was found. This is in accordance with the hypothesis that the two disorders are distinct conditions with independent causes.