the present invention relates to catalyst components for the polymerization of olefins comprising a titanium compound , having at least a ti - halogen bond , and at least two electron donor compounds supported on a mg dihalide , said catalyst component being characterized by the fact that at least one of the electron donor compounds is selected from ethers containing two or more ether groups which are further characterized by the formation of complexes with anhydrous magnesium dichloride in an amount less than 60 mmoles per 100 g of mgcl 2 and by the failure of entering into substitution reactions with ticl 4 or by reacting in that way for less than 50 % by moles , and at least another electron donor compound is selected from esters of mono or polycarboxylic acids . said catalyst components are able to produce propylene polymers which , for high values of xylene insolubility , show a broad range of isotacticity .