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The relaxation of free excitons into the states of bound excitons with large and small radii in lithium hydride single crystals with isovalent and heterovalent impurities has been studied on the basis of low-temperature exciton±phonon spectra of luminescence and resonant combinational scattering. Bound excitons with large radii have resonant levels at E < E ex (E ex is the energy of the basic excitonic state n = 1s) and are characterized by a lifetime not larger than 10 ± ±10 s. The excitons with small radii have lifetimes of 10 ± ±5 to 10 ± ±6 s at 78 K. They may be obtained by either recombination or direct formation of near-impurity excitations or relaxation of bound excitons with large radii into small radii states. Such relaxation takes place due to the generation of LO(G)-phonons.