The paper deals with the properties of hybrid and gradient polymer composites depending on the ratio of different fibers. The major factor governing the rules of composite mechanics is the ratio between ultimate strains of reinforcing fibers. Synergism effects are observed for increasing deformation of carbon fibers under tension and organic fibers under compression when mentioned fibers are located within GFR matrix. Gradient materials with non-uniform structure enable one to assign a rule for varying the material stiffness, which gives an optimal stress distribution in a whole construction under loading.