Objective : Although cognitive-behavior therapy (CBT) is effective in patients with panic disorder, its the-rapeutic mechanism of action in the brain remains unclear. This study was performed to investigate regional blood flow changes associated with successful completion of CBT in drug-naive patients with panic disorder. Method : The regional blood flow in 4 patients with panic disorder was compared to that in 11 healthy controls before and after a 12-week group CBT using $^{99m}Tc$-ECD SPECT imaging. Psychopathology was assessed using Panic Disorder Severity Scale. Data were analyzed using software for statistical parametric mapping (SPM2). Results : Before CBT, significantly decreased blood flow was found in the parietal and occipital area in panic patients than normal volunteers. In all the patients who showed remission after CBT, increased blood flow was detected in the right cingulate gyrus, left lingual gyrus, and left superior parietal lobule, whereas decreased blood flow was seen in the left inferior temporal gyrus. Conclusion : These results suggested that CBT is effective for panic disorder and change the activity of cingulate gyrus and left temporal gyrus, a part of the brain areas associated with fear in panic disorder.