The effects of bath temperature on the electrodeposition of zinc oxide (ZnO) thin films from zinc perchlorate and molecular oxygen, dissolved in dimethylsulfoxide, are reported. The obtained films were highly compact and homogeneous. Scanning electron microscopy images showed that they were formed by nanometric crystallites whose sizes are dependent on bath temperature. Inversely dependence was found between the band-gap (Eg) of the semiconductor with estimated diameters (D) of the crystallites, which corresponds well with quantum confinement effects.