It has been suggested that the pathogenesis of aneurysm in the thoracic aorta may be related to the shape of the aortic arch. In this study,we parametrically constructed computational models of human thoracic aortas based on the geometrical parameters which has been measured from normal subjects and aneurysm patients, and carried out computational fluid dynamics for the blood flow in those models. Our results demonstrate that general wall shear stress (WSS)distributes in a way that regions with relatively high WSS are localized at similar locations consistently among all the models,regardless of whether they are from normal or aneurysm subjects. However, it was found that the peak WSS values within such localized regions tended to be higher in the models from aneurysm subjects. These results imply that such localized regions with relatively high WSS may be candidate sites susceptible to aneurysms because of the focal nature of the aneurysm. Furthermore,it was suggested that the higher WSS at the sites in the aneurysm cases may enhance the possibility for aneurysms.