An adiabatic quantum dynamical model is introduced to solve a paradox with respect to the role of the CO vibration ill the OH + CO(v) -> H + CO2 reaction. The previous agreement of five-dimensional diabatic with six-dimensional results for CO(v = 0), which erroneously Suggested that the CO bond acts as a spectator, is due to a compensation of effects. For CO(v = 1), the reduced dimensionality adiabatic model approximates better the full-dimensional results. Whether AB acts as a spectator in a reaction with X cannot be decided on the basis of a diabatic calculation for AB(v = 0) + X only. (c) 2005 Elsevier B.V.. All rights reserved.