Photodynamic Therapy (PDT) is a method based on the interaction of light with a photosensitizer (PS), localized primarily in cancer-affected tissue, which leads to the formation of cytotoxic oxygen species and the death of cancer cells. The aim of the work was to create new highly efficient antitumor preparations for photodynamic therapy, ternary complexes based on nanoparticles (NP) of zero-valence selenium (Se0), a graft copolymer, and a photosensitizer (Fotoditazin (FD)) were synthesized and investigated. Two types of samples were prepared by introducing the components into the reaction mixture in different orders. The UV spectroscopy studies revealed that spectral characteristics of the formed complexes depended on their preparation method (the order in which the components were introduced into nanodispersion). By means of the UV spectroscopy it was demonstrated that the value of the optical density in the range of PDT wavelength (Q-range) is higher in the triple systems by 30-40% compared to free FD. Visual study of epithelia cells of the African green monkey (Vero) by means of the light microscopy has demonstrated significant inhibition of their growth in all sample wells with the triple complex samples.