This study was designed to evaluate the usefulness of CT angiography using the shaded surface display (SSD) and volume rendering (VR) techniques for diagnosis of the cerebral aneurysms. Forty-seven aneurysms in 38 patients, who diagnosed on conventional angiography were included. All patients under- went the CT angiography using spiral CT and conventional angiography for preoperative evaluation, subsequently. Using VR and SSD techniques, reconstructed angiographic images were obtained. Two radiologists retrospectively analysed the detectability of the two techniques with regard to the lesion's location, size, detectability, shape, direction, and the intraarterial thrombi of aneurysms, compared with conventional angiographic image. Forty five of 47 aneurysms (96%) were detected by CT angiogram, while VR and SSD depicted 45 (96%) and 44 (94%), respectively. With regard to aneurysm shape and direction assessment, SSD was superior to VR. But for depiction of intraaneurysmal thrombi containing calcification, VR was superior to SSD. There is no difference in the detectability between SSD and VR, SSD is somewhat a better technique for discovering the characterizing features, but VR is a very helpful method for demonstrating the intraluminal calcification. Moreover the best choice should be the combination of the two techniques.