The copolymerisation of 1,3-butadiene with ethylvinyl ether and n-butylvinyl ether is discussed. The effect of comonomer ratio on conversion, copolymer composition, microstructure, molar mass and on molar mass distribution is evaluated. Both copolymerisations are characterised by copolymer parameters. The basis of the polymerisations is a heterogeneous Ziegler-Natta-catalyst system.