The aim of the work was to standardize the conditions for obtaining viable and functionally complete cells in the composition of multicellular spheroids (MS). The latter were obtained in the conditions of 7 days 3D cultivation with fibroblasts seeding at concentrations of 1·105, 2·105 and 5·105 cells/ ml. It has been proved that the sowing concentration of fibroblasts affects the size of the formed MS as well as the viability, morphological parameters, proliferative and adhesive properties of cells they are composed of. The maximal concentration that have been used had a negative impact on spheroid formation, on the ability of cells to adhesion. This concentration reduced cell viability by 19%, coefficient of increasing the number of cells 4,25-fold and increased the number of cells with nuclear fragmentation and chromatin condensation by 20% in comparison with the sowing concentration of 2·105 cells/ml. At a concentration of 1·105 cells/ml, predominantly single and small (about 10-20 mkm) MS with a cell viability of about 89,5 ± 1,2% were formed. The fibroblasts had normal morphological characteristics, but the coefficient of increasing the number of cells was significantly lower than the similar indicator at the sowing concentration of 2·105 cells/ml. Thus, it has been established that the concentration of 2·105 cells/ml is optimal for the formation of MS with morphologically and functionally complete fibroblasts.