Objective: This study examined personality subtypes of adults diagnosed with panic disorder (PD). Methods: As part of a National Institute of Mental Health-funded study on personality in a clinical population, randomly selected psychologists and psychiatrists used a Q-sort instrument to describe 96 adults diagnosed with PD. Results: Q-factor analysis yielded 4 personality subtypes: high functioning, emotionally dysregulated, inhibited/avoidant, and somatizing. Within the sample, the subtypes differed on Axis I and H pathology, adaptive functioning, and developmental and family history variables. Personality constellations in the sample showed substantial incremental validity in predicting adaptive functioning and treatment response above and beyond the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Axis 1 diagnoses. Conclusions: These distinctions may elucidate the high rates of comorbidity among patients with PD and are important in understanding treatment choice and outcome. (c) 2009 Elsevier Inc. All rights reserved.