ZnO nanorods were selectively grown on AlN-based substrates by hydrothermal synthesis without employing seed layers. The correlation between ZnO nanorod growth and the dislocation density in the substrates was revealed. Furthermore, the alignment and average diameter of ZnO nanorods were found to be affected by dislocation etch pits exposed on the surface of AlN. A red-shift in photoluminescence emission spectra of ZnO nanorods on etched-AlN was also observed, which can be attributed to the surface effect. (C) 2012 Elsevier B.V. All rights reserved.