A porous CdS:CdO composite structure was formed by screen printing of CdS powder and sintering in air at high temperature. The X-ray diffraction analysis of CdS sintered at different temperatures revealed that a CdO formation in the CdS matrix is by the phase transformation of CdS, which may be stated as CdS-CdSO4-CdO. The structure, composition and photosensitivity of this composite structure depend on the sintering temperature, sintering atmosphere and the flux to semiconductor (FIS) ratio. The results indicate that the screen printed CdS:CdO structure may be used as a photoconductor in solid state devices and as a photoelectrode in phsto-electro-chemical energy conversion systems.