These compositions based on semi-crystalline thermoplastic resin and on ABC block copolymers result in materials or in items which exhibit an impact strength, an elongation at break, a resistance to cracking and to deformation under stress, and a thermal behavior which are improved with respect to semi-crystalline resin or resins alone or mixed with conventional impact additives, while retaining a high modulus and thus a degree of stiffness. They are generally suitable for the preparation of items or articles, such as sheets, films, pipe sheathings, tubings, pipes, yarns, strands, cable sheathings, bracing wires, leaktight sheathings, sleeve tubes, both mono- and multilayer, shaped components, molded panels, thermoformed articles, sections, bottles or powders for coating substrates. The materials or items obtained from these compositions exhibit a characteristic morphology visible in electron microscopy.