Binary compound semiconductor of (CdS) and copper doped (CdS: Cu) thin films have been deposited onto glass substrates at substrate temperature (T =653 K) by spray technique. Different doped films were prepared using different concentrations of Cu (0.1-2%). The effect of copper doping on some physical properties of the prepared films of thickness (0.9 0.05 um) was investigated. The structural, optical and electrical properties of the films have been studied using X-ray diffraction, optical transmission spectra and electrical conductivity respectively. These properties were found to be strongly dependent on the doping concentration. The polycrystalline films with a hexagonal structure for undoped and a mixed (hexagonal+cubic) structure for doped films have been obtained. The optical band gap of these films was found to be decreased from 2.451 to 2.410 eV with increase Cu concentration. The electrical conductivity of these films was found to be decreased initially with increasing Cu concentration, while it started to increase for doping values over 1% of Cu, and a conversion of the conductivity type of the films (from n-type to p-type) was observed at doping level above 1%.