We report on the photo-response behavior of n-ZnO/p-Si photodiodes. Semiconducting n-ZnO films have been deposited on p-Si substrate by RF sputtering at 300, 480 and 550°C. An optimum static photo-response was achieved from the photodiode prepared at 480°C as characterized by photocurrent measurements using a continuous monochromatic red illumination. Temporal photo-response of 35 ns was obtained from the same n-ZnO/p-Si diode to which a high frequency modulation of 1.5 MHz was applied for the dynamic response measurements. It is concluded that the n-ZnO/p-Si photodiode has good detecting capabilities in both of the dynamic and static photo-responses.