This paper is devoted to computer simulations of the optical characteristics (spectral values of the extinction coefficient, scattering coefficient and scattering matrix) of different polydisperse systems of spherical particles relevant to represent various forms of clouds and precipitation (rains, snow, hail) in the spectral region from 0,5 to 10 mm. The calculations are made using the Mie theory formulas [8, 10]. The microstructure parameters and optical constants of the particulate matter are used as the input parameters for simulations.