This study was aimed to assess the comparative capabilities of CT angiography (CTA) and DSA in diagnosing aneurysms in different sites in a series of 20 patients. Volumes were measured during intravenous contrast agent infusion and images were then edited and reformatted as 2D and 3D displays (MPR, SSD, MIP techniques). Some of the main semiologic patterns of aneurysms were considered and the diagnostic accuracy of the 3 reconstruction techniques was assessed and compared with that of axial CT and DSA. Abdominal aortic aneurysms were analyzed separately to study the involvement of main collateral vessels. The best results were obtained with MIP and MPR in the assessment of aneurysm extent and neck. MPR is the only technique which could depict the thrombus and the best technique to demonstrate the relationships between aneurysm and adjacent structures. The MIP technique depicts calcifications and is the method of choice to demonstrate the involvement of collateral vessels by abdominal aortic aneurysms. SSD permits good assessment of the neck and of the longitudinal extent of the aneurysms but is severely limited in the analysis of the other variables.