Cu doped transparent ZnO thin films (CZO) were sputtered on soda lime glass substrates at three different distances between substrate and target. The effects of copper doping on the structural and optical properties were investigated by X-ray diffraction (XRD) and transmittance measurements. The XRD results indicated that CZO thin films have a preferential crystallographic orientation along the hexagonal wurtzite (002) axis. With increasing the distance between substrate-target, from 4 cm to 8 cm, the refractive index of the CZO films decreased. In the visible wavelength region, the average value of the transmittance was above 80%. Thus, significant changes in the structural and optical properties have occurred due to the decrease of the distance between the target-substrate and the residual compressive stress at the film-substrate interface arising during deposition.