Polymer composition showing an improved balance of flexural modulus, IZOD impact strength and elongation at break comprising (percent by weight): A) a polymer blend comprising: A1) 50-70% of a crystalline propylene homopolymer or copolymer; and A2) 30-50% of one or more copolymer(s) of ethylene with one or more C4-C10 α-olefin(s) containing from 15 to 35% of said C4-C10 α-olefin(s); said polymer blend (A) having values of MFR equal to or higher than 10 g/10 min., a total content C4-C10 α-olefin(s) equal to or higher than 8% and an intrinsic viscosity value of the fraction soluble in xylene at room temperature of from 1.3 to 2 dl/g, the amounts of (A1) and (A2) being referred to the total weight of the polymer blend; and optionally B) 1-15% of an elastomeric polymer different from A2), having a hardness (Shore A, ASTM D-2240) value equal to or lower than 90 points; and/or C) 0.5-20% of a mineral filler; the amounts of optional components (B) and (C) being referred to the total weight of the composition.