The authors report on comparative study on ultraviolet (UV) photoconductivity of p-type ZnO:N films and n-type ZnO epilayer. As compared with the ZnO epilayer, the ZnO:N films show much higher photoconductivity but with faster decay. Surface adsorption of C and O, as identified by X-ray photoelectron spectroscopy, is believed to be a major contribution to the UV photoconductivity. The surface adsorption and photodesorption process, combined with a competition between holes and electrons, in p-type ZnO:N, is proposed tentatively, providing qualitative agreement with the observed behaviors. (C) 2007 Elsevier B.V. All rights reserved.