Flow visualization, particle image velocimetry and numerical computation have been complementarily performed to study the fluid flow inside a stented lateral aneurysm. The curved afferent vessel had an inner diameter of 5 mm. The diameters of the aneurysmal orifice, neck and fundus were 7 mm, 5 mm and 7.5 mm, respectively, and the distance between the orifice and dome measured 10 mm. Stents with various porosities were examined. A volume-flow rate waveform of the internal carotid artery was reconstructed with a Wormersley number of 4 and Reynolds number ranging from 202 to 384 in a cardiac cycle. Results are presented in terms of the main and secondary flow velocity vector fields, the inflow rates into the aneurysm and the intra-aneurysmal wall shear stress and pressure. Some comparisons of the computed results with the experimental results and the data available from the literature are also made. It is found that the placement of stents for endovascular treatment is more critical for an unstented parent vessel with curvature than without since the maximum inflow rate of the former is 15 times the latter. The critical porosity of 70% below which an inhibition of intra-aneurysmal thrombus formation will not occur is identified for the first time.