Functional neuroimaging studies have implicated an involvement of the prefrontal cortex and mesolimbic reward system (i.e., ventral striatum) in pathological gambling (PG). However, there is a lack of studies focusing on structural changes in frontostriatal brain regions in adult subjects with PG. In order to study differences in local grey matter volume, 20 male subjects with PG and 21 matched controls underwent structural magnetic resonance imaging. Structural brain data were analysed via voxel-based morphometry with a focus on prefrontal areas and ventral striatum. By comparing grey matter volumes in brain regions highly relevant for brain functional changes in PG, the present study found a higher volume in right ventral striatum and right prefrontal cortex by means of voxel-wise morphometry in PG subjects as compared to controls. Our findings demonstrate local grey matter changes in brain areas that have previously been associated with functional changes in PG. Hypertrophy in the prefrontal cortex might be an adaptation at least partly induced by the higher grey matter volume in the ventral striatum and may help to increase cognitive control over gambling impulses. Future research should explore the relationship between functional and structural alterations as well as the course of changes in PG.