This paper reports on the electrowetting behavior on three micro/nanostructured ZnO (zinc oxide) layers with different roughnesses. ZnO nanorods with diameters of 100 nm and heights of 1 mu m (sample A), 3 mu m (sample B), and micro flower-like layer with a diameter of 5 mu m (sample C) were fabricated on the ITO glass substrates. This was followed by deposition of Teflon to achieve superhydrophobic property on the prepared surfaces. On these three Teflon modified ZnO layers, reversible electrowetting phenomenon was observed on the sample B with applied voltages of less than 40 V, and also on the sample A with a large range of voltage in air environment, but irreversible electrowetting behavior was observed on sample C. The wettability change and reversibility have been analyzed, and it is shown that the differences in the structures of the ZnO layers play a crucial role in the distinct electrowetting performances. (C) Koninklijke Brill NV, Leiden, 2011