The aim of the current study was to use whole brain voxel-based morphometry (VBM) to assess the gray matter (GM) changes in unmedicated patients with obsessive-compulsive disorder (OCD) compared with normal controls. We compared the GM volumes in 28 patients with 22 matched healthy controls using a 1.5T MRI. Three-dimensional T1-weighted magnetic resonance images were obtained from all participants. VBM was performed to detect GM volume differences between the two groups. We detected increased regional GM volumes in the bilateral middle temporal gyri, bilateral middle occipital gyri, bilateral globus pallidus, right inferior parietal gyrus, left superior parietal gyrus, right parahippocampus, right supramarginal gyrus, right medial superior frontal gyrus, and left inferior frontal opercular cortex in the OCD patients relative to controls (P <0.001, uncorrected, cluster size >100 voxels). No decreased GM volume was found in the OCD group compared with normal controls. Our findings suggest that structural changes in the GM are not limited to fronto-striato-thalamic circuits in the pathogenesis of OCD. Temporo-parietal cortex may also play an important role.