The aim of this study is to report the fabrication and the gas sensing properties of ZnO nanostructures. The structures were obtained through electrochemical anodization and post-growth annealing of metallic Zn thin films. The morphology and the crystal structure of the samples were analyzed using scanning electron microscopy, X-ray Diffraction and micro-Raman spectroscopy. Morphological analysis showed that ZnO was obtained in shape of 25 nm diameter nanoparticles connected to each other forming chains. Gas sensing properties towards NO2, H2 and CH4 were investigated too. The structures showed high and reversible response to NO2, H2 and CH4, thus revealing that the obtained architecture of nanostructured ZnO is promising for chemical sensors.