Introduction. Computed tomography angiography (CTA) can add information to digital substraction angiography (DSA) in selected cases of aneurysms of the circle of Willis. Clinical cases. 1. Patient with progressive visual loss and headache. CT and DSA showed an image of partially thrombosed suprasellar aneurysm. CTA better defined the relationship between the lesion and regional vessels. 2. Woman with subarachnoid hemorrhage (SAH). CTA defined the aneurysmal neck and its relationship to the clinoid process. 3. Man with SAH. CT and DSA showed an arteriovenous malformation and three arterial aneurysms one of which was in a tortuous vessel. CTA confirmed digital angiographic data. Conclusion. CTA is a new image technique that can either add or confirm DSA findings in complex aneurysms of the circle of Willis