This study compared the effects of a higher dose of cognitive behavioral therapy (CBT) for panic disorder versus CBT for panic disorder combined with "straying" to CBT for comorbid disorders in individuals with a principal diagnosis of panic disorder with or without agoraphobia. Sixty-five participants were randomly assigned to one of two treatment conditions, either CBT focused solely upon panic disorder and agoraphobia or CBT that simultaneously addressed panic disorder and agoraphobia and, to a lesser degree, the most severe comorbid condition. Results indicated a significant reduction in panic disorder severity and a decline in severity of comorbid diagnoses across both treatment conditions. However, individuals receiving CBT focused only on panic disorder were more likely to meet high end-state functioning at post-treatment, even in intent-to-treat analyses, and report zero panic attacks at the 1-year follow-up, although this effect was not retained in intent-to-treat analyses. At follow-up, CBT focused only on panic disorder yielded more substantial improvement in the most severe baseline comorbid condition, although not in intent-to-treat analyses, and a greater proportion of individuals in this treatment condition were rated as having no comorbid diagnoses, even in intent-to-treat analyses. These findings raise the possibility that remaining focused on CBT for panic disorder may be more beneficial for both principal and comorbid diagnoses than combining CBT for panic disorder with 'straying' to CBT for comorbid disorders.