We describe the successful homoepitaxial growth of ZnO layers on oxygen-face ZnO substrates by metalorganic vapor-phase epitaxy in two-dimensional growth mode. In detail, we discuss the impact of the oxygen/zinc precursor ratio using N2O and O-2 as oxygen precursors, growth temperature, and reactor pressure on structural properties and surface morphology as obtained by X-ray diffraction, field emission scanning electron microscopy, and atomic force microscopy measurements. Optimizing the growth parameters leads to smooth layers, ending up in a mirror-like surface grown in two-dimensional growth mode. The structural layer properties are found to be significantly governed by the substrate properties. (C) 2007 Elsevier B.V. All rights reserved.