Rigidity of expanded polystyrene slabs, which is described by modulus of elasticity, in sandwich is very important in their application. When material is bent it is necessary to determine its bending modulus. Bending modulus is determined according to the force-deflection curve, by fixing loads and deflections. Results of expanded polystyrene slabs bending modulus of elasticity are presented in this article. Bending modulus of elasticity was fixed experimentally by 3 and 4 point bending methods. Possibilities of determination of bending modulus of elasticity dependence on material density or type are shown. Comparison of moduli of elasticity calculated applying 3 and 4 point bending is given also.