Computed tomography and aortography were compared in a retrospective study of 35 patients with aortic dissection of type A (n = 17) and type B (n = 18). Based on classical diagnostic criteria such as evidence of two channels, intimal flaps and displaced intimal calcification, computed tomography was able to confirm the presence and type of aortic dissection in 32 patients. Dynamic computed tomography was used in 20 cases. When bolus technique was applied appropriately (16/20), computed tomography clearly differentiated the two channels and identified each by its time density characteristics. In 5 of the 35 patients included, the aortographic diagnosis was equivocal because no definite second channel was identified. In these, CT was helpful to confirm the diagnosis showing the presence of an intimal flap, displaced intimal calcification and clot in the false channel. It was noted that classical signs of differentiation of the true and false channels by their relationship to intimal calcification and by the anatomic relationship of the two identified channels to each other at different levels of the aorta are not without exceptions. It is concluded that dynamic computed tomography represents a valuable alternative to aortography and is preferred in chronic dissection and follow-up examinations and for the initial workup of patients with a mediastinal mass. However, when a roadmap of the aortic branches is required prior to surgical intervention, aortography remains the procedure of choice.