The work presents the results of Monte Carlo modeling (PHITS) of irradiation of Fe3O4-SiO2-Au nanoparticles – promising agents for enhancing the effectiveness of radiation therapy with X-ray radiation. Within the model of a single nanoparticle in a water phantom, it was shown that, assuming a uniform distribution of gold nanoparticles over the surface of the adhesion layer, the particle density and their size do not have a significant impact on the efficiency of therapeutic X-ray beam conversion. The main factors determining the configuration of dose fields are the chemical composition of the nanoparticles and the energy of the primary photon beam.