Abstract Nanostructured copper oxide films were prepared via sol–gel starting from ethanolic solutions of copper (II) acetate [Cu(CH 3COO) 2·H 2O]. Films were obtained by dip-coating at room temperature in air and were subsequently heat-treated at different temperatures (100–900 °C) in oxidizing (air), inert (N 2) or reducing (4% H 2 in N 2) atmospheres. The evolution of the oxide coatings under thermal treatment was studied by glancing incidence X-ray diffraction, X-ray photoelectron spectroscopy and X-ray excited Auger electron spectroscopy. Different crystalline phases were observed as a function of the annealing conditions. Depending on both temperature and atmosphere, the film composition resulted single- or multi-phasic. All the layers were nanostructured with an average crystallite size lower than 20 nm. The most relevant results concerning sample composition and microstructure as well as their mutual relations with the synthesis conditions are presented and discussed.