After supratentorial infarction crossed cerebellar diaschisis has been described. This report concerns the rare phenomenon of crossed cerebral diaschisis in cerebellar infarction. Relative distribution of cerebral and cerebellar blood flow was measured using three-dimensional, qualitative single-photon-emission-computed-tomography (SPECT) with a rotating gamma camera and 123I-IMP. Regional cerebral blood flow was calculated with the two-dimensional, quantitative 133Xe-inhalation-technique. Reduced uptake was observed in the left cerebral hemisphere (-13.9%) contralateral to the cerebellar infarction with the most marked reduction in the left premotor region (-21%). This might be explained by the functional depression of cerebello-ponto-thalamo-cerebral pathways.