We used ¹¹C-raclopride PET, a marker of D₂ dopamine receptor binding, and statistical parametric mapping (SPM) to localise cortical D₂ receptor dysfunction in individual Huntington's disease (HD) gene carriers (16 symptomatic and 11 premanifest subjects) and assess its clinical significance. 62.5% of symptomatic HD patients and 54.5% of premanifest carriers showed cortical reductions in D₂ binding. The most frequent decreases in cortical binding in individual HD subjects were seen in temporal and frontal areas. Symptomatic HD subjects with decreased cortical D₂ binding had worse scores on neuropsychological tests assessing attention and executive functions than subjects without cortical dopamine dysfunction, notwithstanding comparable reduction in striatal D₂ binding and motor disability. Our results indicate that cortical dopaminergic dysfunction is common in both symptomatic and premanifest HD gene carriers. It is an early event in HD pathophysiology and could contribute to the impairment in neuropsychological performance in these patients.