Zn1-xCdxO thin films were deposited on (0001) sapphire substrates by pulsed-laser deposition. Structural and optical properties of Zn1-xCdxO films were strongly correlated to the processing conditions. The composition of the films varied nonmonotonically as a function of deposition temperatures due to the difference of vapor pressure between Cd and Zn species. The optical energy bandgap of Zn1-xCdxO thin films, measured by photoluminescence and transmittance, changed from 3.249 to 3.291 eV. The change of the optical properties was mainly attributed to the change of the stoichiometry of Zn1-xCdxO, as determined by Rutherford backscattering spectroscopy.