The purpose of this study is to evalute the diagnostic value of the brain scanning and compare the diagnostic accuracy between the scan and carotid angiography. 109 cases which are proved by specific method to each disease, are analized to evalute the diagnostic value of the brain scanning. The 70 cases among the proven 109 case are performed both the scanning and the arteriography and analized to compare the accuracy between the scanning and the arteriography. The results are as follows; 1. The diagnostic accuracy of the brain scanning in the diseases of the central nervous system is 64.2%. 2. The diagnostic accuracy of the brain scanning in the brain tumor is 88%, especially brain abscess. glioma, glioblastoma multiforme, menirgioma and metastic tumor show high positive rate. 3. The diagnostic accuracy in the disease of the brain vessels is 54 %. 4. The comparison of the diagnostic value between the scanning and the arteriography is as follows; 1) The diagnostic value in all diseases of the central nervous system is nearly equal. 2) The diagnostic accuracy in the intracranial tumor is slightly higher in the brain scanning (90.9%) than in the arteriography (81.8%). 3) The diagnostic accuracy in the disease of the brain vessel is higher in the arteriography (77.3%) than in the scanning (54.5%). 5) The diagnostic value when combining the scanning and the arteriography, is 83% in the all central nervous system-lesions, 97% in the cranial tumor and 81.8% in the disease of the central nervous system-vessel. The brain scanning is simple and safe procedure, and moreover has excellent diagnostic value in the diagnosis of the central nervous system lesion.