Difference in integral characteristics of the radiation field calculated using one- and three- dimensional models of a stochastic medium has been studied using approximate asymptotic estimates and Monte-Carlo calculations. For this purpose, standard weighting estimates obtained by Monte-Carlo method are partially averaged analytically over the distributions of the extinction coefficients in a special “Poisson” models of random media. For testing problem with the Henyey-Greenstein scattering phase function, asymptotic and numerical estimates of the transmittance probability obtained were in a close agreement. Moreover introduction of additional horizontal stochastisity decreased both the transmittance and albedo probabilities.