Reduction of energy consumption, improving performance and efficiency is one of the most important factors influencing current trends in the development of components used in the transportation and automotive industry. For car producers, one of the possible ways of achieving such a goal is to reduce the weight of individual components while maintaining or improving the material properties during practical application. Therefore, the requirement of weight reduction also applies to car seat cushions. The use of low-density composite foams using fibrous reinforcements is a suitable solution. These materials have strong nonlinear viscoelastic behavior which is time-dependent. Due to the synergistic effect of foam reinforcement, it is possible to reduce weight while maintaining the corresponding mechanical properties. In this study, numerical simulations were used for analysis and design of the seat cushion with PU foam and composite foam, and their results were evaluated. Mechanical properties of PU foam and composite foam are influenced by internal and external structure, shape and size of the cells, the volume of the filling material, and properties of the used polymer. Mechanical properties e.g. contact pressure, stress distribution, and the dependence of stress on the strain rate are investigated.