Undoped and aluminium-doped ZnO thin films were prepared on glass substrates by spray pyrolysis. The variation in the structural properties with a variation in the zinc acetate concentration in the precursor solution, substrate temperature, as well as the doping concentration, were investigated by means of X-ray diffraction (XRD). The films were found to be polycrystalline, with the (002) orientation being preferential in most of the films. It is clear that the orientation of the crystallites, depends largely on the deposition parameters of the films. It was further found that post deposition annealing under various conditions had no large effect on the structures of the films investigated.