The crystalline properties of zirconia synthesized by the precipitation and sol-gel methods were comparatively studied. Samples were characterized with thermoanalysis and X-ray powder diffraction techniques. The tetragonal and monoclinic crystalline structures of zirconia were refined with the Rietveld technique, which provided the quantitative information concerning the lattice cell parameters, phase concentrations, average crystallite sizes and the concentrations of the cationic and anionic vacancies. Both synthesis methods gave rise to nanocrystalline zirconia. The samples calcined at 800 degreesC and prepared by the precipitation had average crystallite sizes less than 18 nm, which were two times smaller than the corresponding values obtained in the sol-gel samples. Both tetragonal and monoclinic nanocrystalline phases had atomic defects in concentrations that depended on the synthesis method and annealing temperature.