Arterial stenosis, for example Atherosclerosis, is one of the most serious forms of arterial disease in the formation of which hemodynamic factors play a significant role. In the present study, a 3-D rigid carotid artery with axisymmetric stenosis with 75% reduction in cross-sectional area is considered. Laminar blood flow is assumed to have both Newtonian and non-Newtonian behavior (generalized Newtonian fluid), while steady state and pulsatile cases are imposed separately. Governing equations are momentum and continuity. Employing the finite volume technique, flow features such as velocity profiles, flow separation zone and wall shear stress distribution in post stenotic region are calculated. Based on the results of the steady state situation, reverse and circulating flows exist until far from stenosis in Newtonian case. But, in non-Newtonian condition, these regions are limited to smaller areas near the stenosis. As blood flow becomes unsteady, in Newtonian case reverse flows become larger and stronger even far from stenosis while circulating flows weaken. Considering the same assumptions with non-Newtonian behavior, circulating flows become stronger than those of Newtonian model, while reverse flows weaken. Obtained results agree with the analytical results available for Newtonian fluid..