The structural and electronic properties of armchair and zigzag models of single-wall ZnO nanotubes have been investigated by performing semiempirical molecular orbital self-consistent field calculations at the level of AM1 method within the RHF formulation. It has been found that these structures are stable and endothermic. The armchair model has zero net dipole moment, whereas the zigzag model has nonzero net dipole moment. The interfrontier molecular energy gap of these systems are different; the gap of armchair model is about 0.2 eV, whereas the gap of zigzag model is about 4.4 eV. Armchair ZnO nanotubes seem to be conductors, however zigzag ZnO nanotubes seem to be semiconductors. (c) 2005 Elsevier B.V. All rights reserved.