Anxiety disorders are characterized by excessive and irrational fears of common situations that impair normal functioning. Neuroimaging allows researchers to examine brain functioning as people are presented with tasks that provoke or model anxiety. Neuroimaging research suggests that anxiety is moderated by a neural circuit involving three parts of the brain: the amygdala, the insula, and the prefrontal cortex (PFC). Increased activation of the amygdala and insula is associated with high anxiety, although activation of the PFC is thought to reduce anxiety. Cognitive behavioral therapy (CBT) is the only type of psychotherapy with strong evidence for effectively treating panic disorder (PD) and generalized anxiety disorder (GAD), but it only works about half the time. This study will use neuroimaging to examine when and how CBT affects brain functioning in people with PD and GAD. The long-term goals of the research are to develop neuroimaging as a diagnostic tool, to use neuroimaging to predict treatment response, and to understand which changes in brain functioning are related to successful treatment.