Abstract: Objective To evaluate the reliability of 3D-CT angiography (3D-CTA) in diagnosis of aneurysmal subarachnoid hemorrhage (SAH). Methods One hundred and ninety-two patients with acute SAH who underwent CTA in our department from December 2010 to November 2012 were included in this study. Their 3D-CTA images were reconstructed with 3D Slicer software and compared with digital subtraction angiography (DSA) images or intraoperative actual situation. The reliability of CTA was assessed in diagnosis of aneurysmal SAH. Results 3D-CTA showed aneurysm in 162 patients, cerebral vascular malformation in 12 patients, false negative aneurysm in 1 patient, and false-positive aneurysm in 1 patient, which were confirmed by DSA or surgery, with a sensitivity of 96.17% and a specificity of 94.11%. Conclusion 3D-CTA is the first choice of method in diagnosis of aneurysmal SAH.