Hemichorea-hemiballism (HCHB) was infrequently related to cortical lesions such as tumor or infarction. Although functional derangement of the basal ganglia (BG) or the thalamus (Th) was suggested, pathomechanism of HCHB secondary to cortical lesions remains uncertain. We recruited the patients with HCHB secondary to cerebrovascular diseases, excluding other causes such as hyperglycemia. All the patients were studied with brain magnetic resonance imaging/angiography (MRI/MRA) and single-photon emission computed tomography (SPECT). Those with only cortical abnormalities in neuroimaging studies were sorted out as the cases of cortical HCHB. Statistical parametric mapping (SPM) analysis of SPECT was performed to investigate the pathomechanism of cortical HCHB. Ten patients (three males and seven females) were included in our study. Six patients had acute BG lesions with SPECT abnormalities, and one had old BG lesions with abnormal SPECT. Three patients were classified as cortical HCHB with lesions only in the frontal and parietal cortices in MRI and SPECT. SPM analysis revealed additional hypoperfusion in frontal areas, leaving BG and Th free of any perfusion abnormalities. Although cortical HCHB was strictly defined by MRI and SPECT, cortical HCHB was not uncommon (30 %). Further analysis showed intertwined networks among the frontal and parietal lobes for cortical HCHB. Cortical dysfunction is important in the pathogenesis of cortical HCHB even without significant involvement of BG and Th.