In this paper we deal with the flux of aerosol particles on an underlying surface. A relation connecting the instantaneous flux with the instantaneous near-surface concentration is obtained for this (generally speaking, random) value. This made it possible to obtain the expression for the distribution function of the particles’ flux. Using these results, the mathematical expectation, variance, and alternation of the flux are estimated. Some data on the intensity of radio nuclides ascending in the zone of Chernobyl nuclear power plant are taken as input parameters.