A cloud of completely ionized plasma with sources of photons distributed in it is considered. The photon diffusion problem is solved and the distribution of the photons over their escape times is found to be similar to the light curve for X-ray bursters. The solution of the stationary Kompaneets equation is given by the Whitteker function. The formation of radiation spectra due to Comptonization in both cold and hot electron plasma clouds are obtained. The formulae obtained allow the plasma temperature in the region of the main energy release in Cyg X-I source to be determined. The effect of Comptonization on the X-ray iron spectral line profiles strongly depends on the law of photon sources distribution over the plasma cloud.