One of the acute problems of raising the life standard of people nowadays is to protect human skin against harmful UV solar radiation. The aim of this paper is to evaluate the most appropriate size of titanium dioxide (TiO2) fine particles that can be imbedded into the skin in order to achieve the maximal attenuation of the UV-B light. The in-depth distribution in the skin of TiO2 particles achieved with the topically applied sunscreens is determined experimentally by the tape-stripping technique. Computer code implementing the Monte Carlo method is used to simulate photon migration through a 20-μm thick horny layer matrix partially filled with nano-sized TiO2 spheres. Dependencies of the portions of the most harmful UV radiation with the wavelength of 290.5 nm absorbed by and reflected from, as well as transmitted through the horny layer on the concentration of TiO2 particles are obtained and analyzed.