[en] The purpose of the present paper was to establish the influence of the grain size on the determination of the heavy element content by the gamma-gamma scattering method. To solve this problem Monte-Carlo numerical calculations and model measurements were performed. The calculations and measurements were performed for ⁷⁵Se, ¹³⁷Cs, and ⁶⁰Co sources, for lead concentrations of 1%, 3% 5%, and 10%. Grain size was varying in the 0.1 mm to 9.0 mm range. Monte-Carlo calculations and experimental data proved the strong dependence of scattered gamma radiation on the grain size of heavy metal. (author)