The analysis of recent publications shows the widespread use in the biology and medicine of nanoscale compounds with biomimetic and antioxidant activity. Cerium dioxide nanoproducts are considered as a promising nanobiomaterial for biomedical applications because of their high biocompatibility, low toxicity and catalytic activity. The role of Ce3+ soluble salts as bacteriostatic, bactericidal, immunomodulatory and antitumor agents is characterized. The value of nanocrystalline cerium dioxide in protecting cells from oxidative stress is shown. The high efficiency of nano-dispersed cerium dioxide is associated with its oxygen non-stoichiometry, the ability to participate in redox processes in a living cell and its ability to autoregenerate, which is its main difference from classical antioxidants. As a compound what is shown to have a UV-protective effect, different in efficiency for individual tissues, nano-cerium dioxide is shown for use in the treatment of tumor processes, it has a probiotic, antibacterial and antiviral effect. It has been shown that nanocerium can act as a mimetic of superoxide dismutase, catalase, some oxidases, oxidoreductases, and phosphatases, as well as being able to participate in the neutralization of reactive nitrogen. It has been found that, unlike natural enzymes, nanoceria has a more intense effect on the rate of reaction and does not require special environmental conditions, such as a particular temperature and reaction of the environment. The possibility of changing the catalytic activity of cerium dioxide nanoparticles can be achieved by varying their size, dispersion and ligand shell. The presence of more surface defects (surface oxygen vacancies), which stabilize the degree of oxidation of Ce3+, allows cerium dioxide to accumulate and release oxygen from its crystal lattice depending on the environmental conditions. By changing the stoichiometry of nano-dispersed cerium dioxide, its antioxidant and pro-oxidant properties and enzyme activity can be regulated. The use of nanomaterial-based mimetics enzymes creates the ability to reduce the cost of their synthesis, increase catalytic activity and stability under harsh conditions.