Panic disorder and major depression frequently coexist, yet the implications of comorbidity for psychological treatments have rarely been studied. The objective of this study was to evaluate whether pretreatment comorbidity of major depression affects the outcome of cognitive–behavioral treatment (CBT) of panic disorder. Thirty-seven clients who met diagnostic criteria for both panic and major depression participated in 10 sessions of individual CBT for panic. Treatment outcome was contrasted with the outcome of 53 clients having only panic disorder who received the same treatment. The co-occurrence of depression did not adversely affect CBT for panic. These results have implications for clinical practice and theoretical implications for the nature of the relationship between panic and depression.