A catalyst for the homopolymerization or copolymerization of CH2═CHR olefins, made from or containing the product obtained by contacting: (i) a solid catalyst component made from or containing Ti, Mg, Cl, and an internal electron donor compound, wherein the solid catalyst component contains from about 0.1 to about 50 wt % of Bi, based upon the total weight of the solid catalyst component; (ii) an alkyl aluminum compound and, (iii) an external electron donor compound having the formula: (R1)aSi(OR2)b wherein R1 and R2 are independently selected from the group consisting of alkyl radicals with 1-8 carbon atoms and a is 0 or 1 and a+b=4.