Thin films of zinc oxide (ZnO) were deposited on soda-lime (glass) substrate using chemical bath deposition (CBD) technique. The structural and optical properties of the deposited films were investigated using X-ray diffractometer (XRD) and UV- spectrophotometric measurements. The absorption data were used to determine the energy band gap and other optical parameters. It was observed that the films were polycrystalline in nature with high optical transmittance. The energy band gaps were found to vary between 3.09 and 3.45 eV using the absorption spectrum fitting (ASF) method. The influence of molar concentrations on the extinction coefficient, refractive index, real and imaginary dielectric constants was also discussed. The study shows that the optical parameters were greatly influenced by the molar concentrations.