Extensive quantum real wave packet calculations within the helicity decoupling approximation are used to analyze the influence of the HF vibrational excitation on the K+HF (v=0-2,j=0) →KF+H reaction. Quantum reaction probabilities P and reaction cross sections are compared with corresponding quasiclassical trajectory (QCT) results. Disregarding threshold regions for v=0 and 1 (v=2 has no threshold), both approaches lead to remarkably similar results, particularly for , validating the use of the QCT method for this system. When moving from v=0 to v=1 there is a large increase in P and , as expected for a late barrier system. For v=2 the reaction becomes exoergic and P≈0.95 (with the exception of large total angular momenta where centrifugal barriers play a role). While substantial vibrational enhancement of the reactivity is thus seen, it is still quite less than that inferred from experimental data in the intermediate and high collision energy ranges. The origin of this discrepancy is unclear. © 2008 American Institute of Physics.