ZnO tetrapods and ZnO nanorods were synthesized on ZnO nanocrystal substrates by a vapor transport process. The source materials were ZnCO3 powder and ZnO powder, respectively, which were reduced by graphite powder to yield different amounts of the vapor. The catalysts were ZnO nanocrystal layers prepared by successive ionic layer adsorption and reaction method. The effect of the source materials on the structure was investigated. Results showed that for the source of ZnCO3 powder, ZnO tetropds constituted by the four pillarlike ZnO nanorods were obtained, while for the source of ZnO powder a nanorods array was formed. Possible growth mechanism and room-temperature photoluminescence of ZnO nanostructures are discussed. © 2004 American Institute of Physics.