AbstractThe following values of monomer reactivity ratios were found:rS= 3,3 ± 0,3;rB= 0,12 ± 0,02 (cyclohexane, 25 °C). The comparison of the kinetic parameters obtained with Li, Na and K counter‐ions shows that the great difference between coordination polymerization with Li and “typically anionic” polymerization with K is mainly determined by the variation of the cross‐propagation rate constantkBSwith the nature of the counter‐ion. No evidences for the specific role of the solvation of Li counter‐ion with butadiene mono