Deposition temperature, r.f.-power and seed layer deposition time were important parameters effecting the crystallinity of CeO2 thin films deposited by r.f.-magnetron sputtering on Si(100) substrates. The CeO2 (200) peak was notable for a deposition temperature above 600 degrees C. With decreased r.f.-power and thus lower deposition rate, the intensity of the CeO2(200) peak increased. When the seed layer deposition time was less than 20 s, the CeO2(200) peak dominated. Transmission electron microscopy (TEM) diffraction revealed that the deposited CeO2 thin film had a polycrystalline structure. Annealing at 950 degrees C in O-2 atmosphere for 30 min increased and sharpened the CeO2(200) peak.