Process for the preparation of ethylene copolymers comprising the copolymerization of ethylene with olefins CH.sub.2.dbd.CHR, in which R is a hydrocarbyl radical with 1-12 carbon atoms carried out in the presence of a catalyst comprising (i) a solid catalyst component comprising Mg, Ti, halogen and specific 1,3-diethers of formula (I) in which R is a C.sub.1-C.sub.10 hydrocarbon group, R.sub.1 is methyl or ethyl, optionally containing a heteroatom, and R.sub.2 is a C4-C12 linear alkyl optionally containing a heteroatom, and (ii) an organo-Al compound. The obtained copolymers are endowed with good comonomer distribution. ##STR00001##