Undoped zinc oxide nanostructured layers were prepared on glass substrates by the spray pyrolysis technique using 0.1– 0.2 mol/l aqueous solution of Zn(CH3CO2)2.2H2O in the temperature range 350–570°C. The nanostructured layers were characterized by SEM, XRD and UV-VIS spectrophotometry. A nanostructured layer evolved into the form of single crystalline hexagonal prisms with the formation of nanorods at different deposition temperatures. The increase of the deposition temperature and of the solution concentration had a significant influence on the nanorod dimensions. We found that the formation of flower-like deposits occurred at 550°C. X-ray diffraction revealed that the ZnO nano-structured layers growing from 0.1 and 0.2 mol/l in the temperature range 450–570°C were c-axis-oriented with the (002) orientation in most of the samples. UV-VIS investigation showed the dependence of refractive indices and thickness on the deposition temperature.