ZnO 2 hollow nanospheres and nanotubes were synthesized via hydrothermal treatment of ZnO submicron-sized powder in 20vol.% H 2 O 2 aqueous solution at 120°C for 6h, and ZnO with similar hollow nanostructures could be obtained by thermal decomposition of the hydrothermally-synthesized ZnO 2 hollow nanospheres and nanotubes in air at 200°C for 6h. The possible formation mechanisms of the ZnO 2 and ZnO hollow nanostructures were proposed. The present work pointed out a simple, cost-effective and green way of converting bulk ZnO powder into hollow-nanostructured ZnO 2 and ZnO powders. The as-synthesized hollow-nanostructured ZnO 2 and ZnO powders have promising uses as catalysts, adsorbents and light weight fillers, etc.