The present work summarizes the results of the study of different tracks of X-ray photons radiative relaxation in a number of multi component oxides. Al 2BeO 4, Be 2SiO 4, Al 3Be 2Si 6O 18 crystals form a group of compounds characterized by similar cation radii but different in the symmetry of the cation-oxygen tetrahedral. Y 2SiO 5, Gd 2SiO 5, La 2Be 2O 5 crystals form another group of compounds differ in cation radii in different crystal sublattices and characterized by the presence of d-states in the bottom of conduction band. It is determined that for Al 2BeO 4, Be 2SiO 4, Al 3Be 2Si 6O 18 crystals the fast relaxation of cation excitons appearing when the crystal absorbs the quantum with energies near the K - or L -edges of the crystal-forming cations of Al, Be and Si is observed only if the symmetry of the local crystalline unit nearing the cation is lowered. When the experiment is carried out with the crystals containing heavy cations (Y 2SiO 5, Gd 2SiO 5, La 2Be 2O 5) the fast relaxation for neither cation nor anion excitons (nor the associated deformation of the crystal lattice) is observed near the light cations. The presence of d -states in the bottom of conduction band is most possible reason of this experimental fact. The excitons appearing in this process are characterized by a heavier (trapped) electronic component and that makes the following exciton relaxation energetically more efficient in comparison to the relaxation of excitons with the electronic component formed by the s - or p -orbitals of light cations.