ZnO nano-islands, with much more uniform size, have been grown through two-step method by metal organic chemical vapor deposition (MOCVD). The room temperature band-edge UV emission intensity of nano-islands was usually undetectable or much smaller than that of thin film. Photolummescence (PL) emission of those nano-islands shows the high intensity nearly as that of ZnO thin film, which is great different from previous reports. By meaningfully analyzing both PL and growth condition of those three samples (bulk ZnO wafer, nano-islands and film), neutral-donor-bound-exciton ((DX)-X-0) emission observed on ZnO nano-islands sample is eventually attributed to hydrogen and aluminum, respectively. The abnormal phenomenon of nano-islands PL intensity has been explained by the point of zinc vacancies (V-Zn) complex defects. It is considered to govern the nonradiative combination and lead enhanced intensity of UV emission in ZnO nano-islands. (c) 2006 Elsevier B.V. All rights reserved.