Thin ZnO films were deposited at room temperature on glass substrates by a pulsed filtered cathodic vacuum arc deposition system. The crystallographic structure and the size of the crystallites in the films were studied by means of x-ray diffraction. These measurements show that all the films are crystallized in the wurtzite form, present in a preferred orientation along the ( 002) direction, and the grain size is estimated to be 18.9 - 42 nm. The crystallite sizes were found to increase and the x-ray diffraction patterns were sharpened by annealing. Optical properties of the ZnO films were studied using a UV-visible spectrometer and calculations made using the envelope method. The absorption coefficient and optical band gap of the films were increased while the refractive index was decreased by annealing. The best annealing temperature for pulsed cathodic vacuum arc deposition grown ZnO thin films on glass substrates was found to be 600 degrees C from optical properties. This temperature is as high as can be measured for glass substrates samples because of the glass properties.