Catheter-based intra-arterial digital subtraction angiography (IADSA) is widely trusted for diagnosing cerebral aneurysms. However, three-dimensional CT angiography (3D-CTA) is evolving. This study compares the diagnostic performance and inter-rater reliability of 64-slice 3D-CTA and IADSA. Nineteen patients with 26 suspected cerebral aneurysms (23 with confirmed aneurysms, three negative controls) underwent both IADSA and 3D-CTA. Two independent reviewers assessed both imaging modalities for the presence of an aneurysm and subsequently described aneurysmal location, size, shape, orientation, and number of emanating arteries. Inter-observer agreement was followed to control for observer bias. The sensitivity of 3D-CTA was 78% and 96%, the negative predictive value (NPV) was 38% and 75%, and the accuracy of 3D-CTA was 81% and 96%. Both reviewers found 100% specificity and 100% positive predictive value (PPV). There was a clear correlation between 3D-CTA and IADSA for describing cerebral aneurysms. The authors conclude that 3D-CTA has equivocal diagnostic advantage but is less reliable for ruling out aneurysm presence. Anatomy, however, is superior with 3D-CTA.