X-ray diffraction and simulation of the data were used to characterize simultaneously sputtered specimens of Co/Cu multilayers. It is shown that a simple geometrical factor, namely, the difference in the mean distance between the sputtering targets and the samples leads to noticeable changes in magnetoresistance due to variations in the structural parameters. The variations, especially the enhanced interfacial roughness of the Co layers, may induce contacts between neighboring Co layers that decrease drastically the absolute value of the magnetoresitance.