[en] The scintillation process in rare gas (RG) and its condensed phases has been theoretically considered. On the base of data on scintillations in RG gas phase it has been found that RG scintillations comprise two components (slow and fast) locating in different spectral range. The fast component duration constitutes 7x10^-9 s in xenon and makes main contribution to the scintillation intensity in the near ultraviolet and visible light regions. The slow component is related to the vacuum ultraviolet region and its duration decreases with gas pressure growth. Thus slow component duration in xenon at the 0.8x10⁵ Pa pressure equals 10^-7 s and at the 41x10⁵ Pa pressure - about 1.8x10^-8 s. The maximum attainable values of RG conversion efficiency are estimated and they are compared with experimental data. Calculation values of average energy necessary for one photon production; ionization potentials; emitted quanta energies and conversion efficiency for argon, xenon and crypton are given. Theoretical value kappa for xenon equals 13.7% and the experimental one - 12.5%. The scintillation process in condensed rare gases is described which is considered as a strongly compressed gas. It is pointed out however that for the condensed gas there exist specific effects which have no analogs in a gas phase. Theoretical value kappa for condensed xenon constitutes 62.6% and the experimental one equals 14%. Such a discrepancy between theory and experiment proves a considerable role of non radiation transitions in the energy transformation process in a substance. The investigations carried out have shown that condensed RG base scintillators have a good time resolution and high efficiency and can be successfully employed for gamma detection