The paper proposes an approach to determining the value of rotational inertia per unit volume for models that take into account microrotation of medium microparticles. Such an approach will allow extending the use of the Cosserat couple continuum for modeling the distribution of deformations and stresses in rigid and flexible foam materials. A series of experimental studies of polyurethane foam samples under compressive and bending loads was conducted. The microstructure of foam materials was analyzed based on cross-sections of samples before and after deformation. Models of deformation of the cellular structure of polyurethane foam under compressive and bending loads were developed. Two approaches to choosing the value of rotational inertia per unit volume are proposed. The optimality of each of these approaches can be determined by comparing the results of modeling analysis of the distribution of deformations in foam and other structurally inhomogeneous materials with the data of experimental studies. The proposed approach allows for a more accurate analysis of the stressed and deformed state for different classes of structurally inhomogeneous materials.