PURPOSE: Our hospital introduced an intraoperative computed tomography (CT) for reasons such as its broad utility, safety and economy, despite an increase in intraoperative magnetic resonance imaging (MRI). We would like to verify existence value of our intraoperative CT system for neurosurgical procedures. MATERIALS AND METHODS: We performed intraoperative CT scans for the patients with 16 gliomas and 1 anterior cerebral artery partially thrombosed large aneurysm, which was treated by A2 side to side anastomosis and proximal occlusion, using a CT with 900mm opening size, radiolucent skull clamp and three types of pin made by stainless, titan, and sapphire, respectively. We assessed the residual tumors with plain and enhanced CT scans. In the cases of non-contrast tumors, small titan clips were applied on the wall of resection cavity to clarify the residual tumors. We also use 3-dementional CT angiography (3DCTA) for evaluating the hemodynamics. The time from the preparation to take images to restarting operation, image quality including the amount of halation caused by pins, and incidence during these procedures, were evaluated. RESULT: We could obtain CT scans all of these cases, regardless of the patients' position. All the surgical instruments were just put on the table below the breast. The amount of halation with sapphire pins was minimum, however even with them, it was difficult to evaluate the detailed residual tumors just beneath the location of pins. CTA was useful, especially for demonstrating the hemodynamics after resection of insulo-opercular gliomas and bypass/clipping. Total time to take CT scans was 15–40 (mean, 27) minutes. There had occurred no incidence including anesthesia. CONCLUSION: MRI is better than CT at the point of spatial resolution, but CT can be defined as an useful system in its easy-to-use, safety, and vascular evaluation.