In the present work, n-ZnO/p-8HQ and n-CdS/p-8HQ thin film heterojunctions were fabricated using spin coating and chemical bath deposition (CBD) techniques, respectively. The letter n indicates that the film is an n-type semiconductor, and the letter p is a p-type semiconductor. The thin films of ZnO covered with 8-hydroxyquinoline (8HQ) and CdS covered with 8HQ were investigated for electrical characteristics. The crystal structure of the films was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The optical properties of the films were investigated through a ultraviolet-visible spectrophotometer (UV-Vis spectrometer). The experimental results show that the conduction mechanism in the films is ohmic. The experimental results also reveal that ZnO thin films have diode properties with 8HQ while CdS does not have diode properties with 8HQ.