The distribution of personality disorders (PDs) was explored in hospital-treated subjects and in a population subsample. This study forms a part of the Northern Finland 1966 Birth Cohort study. Hospital case records of psychiatric treatment periods of all cohort members (n=11,017) were reviewed and re-checked against DSM-III-R criteria. A subsample of the cohort members living in Oulu (n=1609) were invited to a two-stage psychiatric field survey with Structured Clinical Interview for DSM-III-R (SCID) as a diagnostic method. The most common PDs in hospital-treated sample were cluster B PDs (erratic). In the population subsample, cluster C PDs (anxious) formed the majority.