Many voxel-based morphometry (VBM) studies have found abnormalities in gray matter density (GMD) in obsessive-compulsive disorder (OCD). Here, we performed a quantitative meta-analysis of VBM studies contrasting OCD patients with healthy controls (HC). A literature search identified 10 articles that included 343 OCD patients and 318 HC. Anatomic likelihood estimation meta-analyses were performed to assess GMD changes in OCD patients relative to HC. GMD was smaller in parieto-frontal cortical regions, including the supramarginal gyrus, the dorsolateral prefrontal cortex, and the orbitofrontal cortex, and greater in the basal ganglia (putamen) and the anterior prefrontal cortex in OCD patients relative to HC. No significant differences were found between children and adults. Our findings indicate differences in GMD in parieto-frontal areas and the basal ganglia between OCD patients and HC. We conclude that structural abnormalities within the prefrontal-basal ganglia network are involved in OCD pathophysiology.