On aluminium single crystals with (1 1 1), (1 1 0) and (1 0 0) orientation, nanoporous alumina layers were formed in a two-step anodization process within sulphuric acid. The pore ordering within the hexagonal arrangement of the nanopores was documented by scanning electron microscopy (SEM), described on the basis of defect thermology and analyzed quantitatively by image evaluation. The best ordering was obtained in nanoporous alumina on (1 0 0) aluminium. We supposed that this is caused by the interface energy term within the driving force for the formation of the nanoporous alumina, since - in contrast to (1 1 1) and (1 1 0) aluminium as substrate - in the case of (1 0 0) aluminium the interface energy is minimised in the waved interface between aluminium and hexagonally arranged nanoporous alumina. (C) 2011 Elsevier B.V. All rights reserved.