The problem of measuring the parameters of dust particles in the environment is currently relevant for residents of densely populated cities. Measurements of the size and size distribution function of dust particles are carried out using instruments based on the method of scattering of laser radiation. The analysis of the measurement method based on the spherical particle model and the theory of Mie diffraction theory is carried out. The indicatrices of laser radiation scattering by particles 2.5 and 10 μm in size are calculated. The size distribution function of particles is estimated under the condition that the intensity of scattered laser radiation is measured for at least two scattering angles. The possibility of erroneous indication of measurement results by widely used portable measuring devices for dust parameters is shown.