An elastomeric thermoplastic polyolefin composition comprising (I) a crystalline propylene polymer containing at least 80% by weight of a fraction insoluble in xylene at room temperature, the intrinsic viscosity being higher than 0.5 dL/g; (II) an atactic or amorphous propylene polymer having an intrinsic viscosity higher than 0.5 dL/g; and (III) an elastomeric olefin polymer comprising copolymers of ethylene with a comonomer selected from C3-C8 null-olefins, the intrinsic viscosity ranging from 1 to 4 dL/g. In said polyolefin composition the density of the elastomeric olefin polymer (deOP) satisfies the following relationship:deOPnull0.005nullnulldcPPnullnullwcPP/(wcPPnullwaPP)nullnullnullnulldaPPnullnullwaPP/(wcPPnullwaPP)nullnullnullnull(1)wherein wcPP and waPP are the weight percentage content of components (I) and (II) respectively and dcPP and daPP are the density at room temperature of components (I) and (II) respectively.