A process for obtaining porous propylene polymers optionally containing up to 10% by mol of derived units of one or more alpha-olefins of formula CH2═CHZ wherein Z is H or a C2-C10 alkyl radical, comprising the step of polymerizing propylene and optionally said one or more alpha olefins, under polymerization conditions, in the presence of a catalyst system comprising at least a metallocene compound, said process being characterized in that: a) the catalyst system is supported on an organic porous polymer; and b) at least part of the polymerization reaction is carried out in the presence of hydrogen.