Three-dimensional (3D) endoscopic-mode software was used at helical computed tomography (CT) to evaluate distal aortic arch aneurysms (n = 12) and aortic dissections (n = 10); images were compared with two-dimensional (2D) axial source images. In distal aortic arch aneurysms, the 3D endoscopic mode depicted the relationship of the arterial orifices and the aneurysm, which is difficult to evaluate with 2D axial images alone. In aortic dissections, however, the 3D endoscopic mode did not provide additional information to that provided on the 2D axial source images.