Exact wave packet calculations are carried out to investigate the effect of vibrational excitation of the reagent bonds on the dynamics of the CN + H₂ → HCN + H process using the multiconfiguration time-dependent Hartree algorithm. The results are compared to the approximate theoretical and the available experimental results. The differences between the results of the theoretical studies are discussed from the point of view of an approximate or exact kinetic energy operator used in the quantum mechanical studies. Deviations between exact theoretical and experimental results points to the inaccuracies of the potential energy surface used.