Radiation angiopathy was developed by the process of accelerated atherosclerosis at the site of irradiation. The case of a 44-year-old man with right hemiparesis showing a high signal intensity in the left semioval center on MRI and a defect in the left temporo-parietal area with subsequent filling-in with I-123 IMP brain SPECT is reported. Digital subtraction angiography showed typical radiation angiopathy with ulceration in the left common carotid artery. Twenty-four years previously, he underwent curative irradiation of a neck mass that revealed Hodgkin's disease by biopsy. The emboli formed at the site of radiation-induced angiopathy and caused cerebral infarction. The perfusion abnormality in the territory of the embolic artery was detected by I-123 IMP SPECT. Long-term survivors of neck irradiation are at high risk for the development of carotid arterial disease and should be watched carefully.