We have investigated the influence of deposition order of spin-valve (SV) layers on the giant magnetoresistance and magnetic domain structures of top-deposited Si-Ta-Co-Cu-Co-Ir20Mn80-Ta (TSV) and bottom-deposited Si-Ta-Ir20Mn80-Co-Cu-Co-Ta (BSV). The TSV has a maximum MR ratio of about 9.6%, whereas that of the BSV is about 3%. Magnetooptical imaging revealed that the magnetization reversal of both samples occurs by nucleation, extension, and annihilation of microsize domains. It was found that, unlike the TSV, the BSV changes its unidirectional anisotropy in an applied magnetic field. The difference in the domain behavior and in the GMR of the spin valves with top and bottom antiferromagnetic layer deposition could be attributed to differences in defect structures.