ZnO films have been prepared on indium tin oxide-coated glass substrates, with the help of a potentiostatic method in aqueous zinc nitrate solution. Dependence of crystallographic, optical and electronic properties on thickness of the film is reported and discussed. An increase in the film thickness causes an increase in the band and leads to an improvement in crystallinity and conductivity. The experimental results suggest a strong correlation between electronic and crystal structure of the polycrystalline wurtzite ZnO films. These observations can be used to establish guidelines for optimizing the thickness and orientation to increase the control of device performance based on ZnO thin films.