Nanostructured ZnO films on glass substrate were studied by nanoindentation, scanning electron and atomic force microscopy. The films were obtained by a straightforward mechanoactivated oxidation method. The morphology of the obtained films was grained with a grain size in the range 50-100 nm and the thickness was approximately 2 pm. A detailed deformation behavior of ZnO films, critical parameters and indentation induced plastic deformation mechanisms were determined in correlation to bulk ZnO, Si single crystal and commercial ZnO films. In comparison to a single crystal ZnO, nanostructured films exhibit increased hardness (9 GPa); however, the Young's modulus is decreased (120 GPa). A directly detectable evidence of brittleness, "pop-in" and "pile-up" phenomena in ZnO films was not observed. The ZnO/glass interface is stable and exhibits high adhesion, no signs of delamination or presence of brittleness cracks were detected (even at load P-max > 2 N). The role of grain boundaries on the properties of deformation behavior of ZnO nanostructured films has been discussed. (C) 2011 Elsevier B.V. All rights reserved.