CT findings of cerebrovascular diseases were studied in 111 patients with atrial fibrillation (Af). One of these patients had cerebral hemorrhage, and another, subarachnoid hemorrhage, while the others all had cerebral infarctions. CT revealed 122 lesions with a low-density area (LDA) in 105 patients. Based on the cerebral artery territory, the 122 CT lesions were classified into the following 8 types: 10 hemispheric, 43 superficial, 23 deep, 28 superficial+deep, 1 anterior cerebral artery, 6 posterior cerebral artery, 10 watershed, and 1 vertebrobasilar. Therefore, infarctions of the internal carotid artery (ICA) system, including 94 infarctions of the middle cerebral artery territory, were most frequent, accounting for 94% of all lesions. The ratio of the left to the right infarctions of the ICA system was 1.1:1. However, it should be noted that non-embolic infarctions can occur even patients with Af.