The present study investigated the effects of personality disorders (PDs) and specific PD-related beliefs on the results of (cognitive-) behavioral therapy for anxiety disorders in a sample of 398 outpatients. The authors used a prospective design in which relationships between PD variables before treatment and outcome measures at posttest and follow-up were evaluated with multilevel analyses. People with PDs and PD-related beliefs reported higher symptom levels at outcome. However, these effects were not as strong as might be expected on the basis of prevailing clinical thought in this area. Dropout rates were not influenced by the presence of 1 or more PDs or PD-related beliefs. Results indicate that treatment of anxiety disorders in patients with concomitant one or more PDs is appropriate.