The behavior of a signal—to—noise (S/N) ratio is investigated depending on the optical dimensions of a medium and the quantum survival probabilities as well as the influence of the underlying surface and external sources is analyzed during radiation propagation through a multilayered medium. It has been shown that absorption by a medium affects the signal—to—noise ratio impoving it by a few orders of magnitude. The influence of the layered structure on the dependence of the S/N ratio upon the optical size of a scattering volume is also analyzed.