Using the SCF MO LCAO (self-consistent MO LCAO method in the Mulliken-Wolfsbergelmholz approximation) cluster method and the Green's function method in the ASA-KKR (Korringa-Kohn-Rostoker method in the atomic spheres) approximation, the effect of substitutional impurities (O, C, B, Be, He) on the electronic structure of titanium nitride has been studied. The distributions of the local electronic states of impurity centers and the location of impurity levels in the total energy spectrum of the crystal have been calculated. A detailed discussion is presented of how the entire system of chemical bonding near a defect and the partial interatomic interactions vary as a function of the nature of the impurity atom. The results obtained are employed to interpret the available X-ray emission spectra of ternary systems, and also in treating problems of the mutual solubility of refractory binary phases and heterogeneous catalysis with their participation. A quantum chemical simulation of possible hydrogen atom positions in the nitride structure has been carried out. Hydrogen has been found to occupy preferentially tetrahedral interstices of the TiN lattice.