Crystalline cerium(III) phosphate (CePOsub.4), cerium(IV) phosphates, and nanocrystalline ceria are considered to be promising components of sunscreen cosmetics. This paper reports on a study in which, for the first time, a quantitative comparative analysis was performed of the UV-shielding properties of CePOsub.4, Ce(POsub.4)(HPOsub.4)sub.0.5(Hsub.2O)sub.0.5, and CePOsub.4/CeOsub.2 composites. Both the sun protection factor and protection factor against UV-A radiation of the materials were determined. Ce(POsub.4)(HPOsub.4)sub.0.5(Hsub.2O)sub.0.5 was shown to have a sun protection factor of 2.9, which is comparable with that of nanocrystalline ceria and three times higher than the sun protection factor of CePOsub.4. Composites containing both cerium dioxide and CePOsub.4 demonstrated higher sun protection factors (up to 1.8) than individual CePOsub.4. When compared with the TiOsub.2 Aeroxide P25 reference sample, cerium(III) and cerium(IV) phosphates demonstrated negligible photocatalytic activity. A cytotoxicity analysis performed using two mammalian cell lines, hMSc and NCTC L929, showed that CePOsub.4, Ce(POsub.4)(HPOsub.4)sub.0.5(Hsub.2O)sub.0.5, and nanocrystalline ceria were all non-toxic. The results of this comparative study indicate that cerium(IV) phosphate Ce(POsub.4)(HPOsub.4)sub.0.5(Hsub.2O)sub.0.5 is more advantageous for use in sunscreens than either cerium(III) phosphate or CePOsub.4/CeOsub.2 composites, due to its improved UV-shielding properties and low photocatalytic activity.