Well-aligned ZnO nanorod at-rays were synthesized on the c-axis orientated ZnO seed layer by chemical bath deposition (CBD) technique. Randomly distributed ZnO microrods with big diameter and growth speed were also formed simultaneously in the same process. The growth of the microrods followed the expected diffusion-limited Ostwald ripening mechanism reasonably well, while that of the nanorods was suggested to be controlled not only by the nutrition ions available but also by the density of nuclei site and the reaction kinetics on the growing surfaces, etc. The microstructure and optical properties of the well-ordered nanorod were also investigated. (C) 2009 Elsevier Ltd. All rights reserved.