The vector equation of radiation transfer and its scalar approximation are considered, as well as the principles and results of Monte Carlo modeling of elements of the light scattering matrix (LSM) during the propagation of polarized light in multiple scattering media. The amplitudes and angular dependences of the normalized elements of the LSM are calculated. The theoretical results of this chapter serve as a confirmation of the preferential preservation of certain types of polarization under conditions of multiple scattering for different sizes of scattering particles or tissue structures. The limits of applicability of the single scattering approximation for interpreting the results of experimental studies are estimated. The Monte Carlo method for calculating photon trajectories was used to simulate polarization effects under multiple scattering in a system of randomly located scattering particles. The specificity of densely-packed particle systems is also analyzed. Data are presented for tissue parameters: absorption coefficient, scattering coefficient, scattering anisotropy factor, and refractive index of individual tissue layers, which are necessary for calculating polarization properties under conditions of multiple scattering.