Background: Tics in Gilles de la Tourette syndrome (GTS) are repetitive patterned movements, resembling spontaneous motor behaviour, but escaping voluntary control. Previous studies hypothesised relations between structural alterations in prefrontal cortex of GTS adults and tic severity using voxel-based morphometry (VBM), but could not demonstrate a significant association. The relation between prefrontal cortex structure and tic inhibition has not been investigated. Methods: Here, we used VBM to examine 14 GTS adults without associated comorbidities, and 15 healthy controls. We related structural alterations in GTS to clinical measures of tic severity and tic control. Results: Grey matter volumes in the right inferior frontal gyrus and the left frontal pole were reduced in patients relative to healthy controls. These changes were not related to tic severity and tic inhibition. Conclusion: Prefrontal grey matter volume reductions in GTS adults are not related to state measures of tic phenomenology.