Cathodoluminescence (CL) with energy-controlled electron beams was used to study the inner structure of ZnO nano-phosphors fabricated by YAG laser ablation under oxygen gas and oxygen plasma circumstances. Varying accelerating voltages of electron beams from 1.0 to 3.0 kV, it was clearly seen that the CL spectrum in the case of ZnO nano-phosphors fabricated under the oxygen gas background changed from a broad one centered at approximately 500 nm to a narrow one peaked at 380 similar to 400 nm. This result indicates that there is an oxygen vacancy-rich shell in the surface area and a fine crystalline ZnO structure in the inner core region. Under the oxygen plasma circumstance at 500 Pa, however, we found that there is a crystalline structure in the surface layer of ZnO nano-phosphors due to the sufficient supply of oxygen ions and atoms and suppression of the formation of oxygen vacancy. (C) 2009 Elsevier B.V. All rights reserved.