In the paper the results of the mathematical modelling a horizontal two-phase turbulent round jet carrying coarse solid particles are presented. The numerical results are compared with the experimental data obtained in our laboratory. The goal of these investigations is to describe the distribution characteristics of the mass concentration of particles moving with a velocity lag which starts from the pipe outlet. These features are based on the intensive diffusion of particles with the rapid decrease of their concentration from the initial stage of the jet (scattering effect) and the less intensive diffusion giving a wave-like distribution of the mass concentration along the axis of the jet (intermediate effect). Such particle distributions in the jet are related to the specific motion of coarse particles in the pipe expressed by their lagging behind the gas. For the mathematical description, an algebraic model for the closure of the equations for the dispersed phase which is based on the inter-particle collision is used since the solid admixture in our experiments is a polydispersed powder. Along with the inter-particle collision, turbulent interaction between the phases resulting in the Reynolds stresses in the dispersed phase is also taken into account. In addition, the Magnus lift force contributes to the model due to the particle rotation and the velocity lag of the particles which enter the jet.