The rates of comorbid personality disorders in patients with panic disorder are reported to be elevated, have an adverse impact on the response to treatment, and increase the likelihood of relapse on treatment discontinuation. We examined the rates of personality disorders in panic disorder patients in a longitudinal, naturalistic study of panic disorder. Of 100 panic disorder patients studied, 42 met criteria for at least one personality disorder as determined by the Personality Disorder Questionnaire-Revised (PDQ-R). The presence of a personality disorder as determined by the PDQ-R was associated with a past history of childhood anxiety disorders, comorbidity with other anxiety disorders and depression, and a chronic, unremitting course of panic disorder in adulthood. The presence of a personality disorder in these patients was not significantly associated with a history of physical or sexual abuse in childhood. Our findings support the notion that an anxiety diathesis, demonstrated by significant difficulties with anxiety in childhood, influences the development of apparent personality dysfunction in panic patients. In other cases, personality pathology may reflect the presence of comorbid anxiety disorders or depression. The association of personality disorder in panic patients with a more unremitting course of illness underscores the importance of axis II pathology in understanding the longitudinal course of panic disorder.