The morphology of yttria doped zirconia thin films deposited by metal organic chemical vapour deposition (MOCVD) in two different substrate materials, glassy quartz and sapphire single crystals has been examined. The Y2O3 doping concentration has been varied from 3 to 12 mol percent. Structural characterization has been realized by X-ray diffraction, raman spectroscopy and scanning electron microscopy. The structure of the films corresponds to that of bulk crystals of the same composition. Refractive index has been determined by the optical transmission method. Refractive index close to those of bulk crystals are obtained for epitaxially grown zirconia on sapphire substrates, whereas low refractive index values, related with low packing densities, are obtained for thin films in the glassy substrate.