This study examines whether specific sets of dysfunctional beliefs are differentially associated with five personality disorders (PDs) as predicted by cognitive theory. Seven hundred fifty-six psychiatric outpatients completed the Personality Belief Questionnaire (PBQ) at intake and were assessed for PDs using a standardized clinical interview conducted by assessors who were blind to patients' PBQ responses. Findings showed that patients with avoidant, dependent, obsessive-compulsive, narcissistic, and paranoid PDs preferentially endorsed PBQ beliefs theoretically linked to their specific disorders. The study results support the cognitive theory of personality disorders. Suggestions are made regarding the clinical utility of the PBQ with personality-disordered patients and future research on the PBQ.