We have studied the giant magnetoresistance of two sputtered systems, Co/Cu multilayerswithandwithoutFe buffer layers, with respect to their magnetic and structural properties. A different oscillatory character of the magnetoresistance as a function of Cu interlayer thickness was found for these two series. The specimens were magnetically characterized using a vibrating sample magnetometer. Transmission electron microscope cross‐sectional images and low‐angle x‐ray diffraction analysis indicated a very different quality of the multilayer structure for these two systems. This is assumed to be the reason for their different magnetoresistant behavior.