Rubber-reinforced vinyl aromatic polymers having a strictly bimodal morphology, comprising from 55 to 90% by weight of a rigid polymeric matrix and from 10 to 45% by weight of a rubbery phase dispersed inside said rigid polymeric matrix, in the form of grafted and occluded particles and wherein said rubber particles consist of from 60 to 99% by weight of particles with a capsule or “core-shell” morphology and from 1 to 40% by weight of particles with a “salami” morphology, said percentages being measured on the basis of the weight of the rubber particles only.