Hydrogenation of unsaturated carbon-heteroatom bonds, C=X, is the general process for which we assess consistency of quantum chemical calculations in the context of B(C6F5)(3)-catalyzed reduction of imines with H-2. According to the mechanism of the reaction, computational uncertainty of energies of hydrogenation of imines, i.e. the difference between results obtained with different methods, contributes to method-related uncertainties of the computed relative energies of key H-2-activating species. For this reason, it is desirable to know the magnitude of methodological dependence/uncertainty of energies of hydrogenation. Calculations were performed with a number of different density functionals, such as M05-2X, M06-2X, B3LYP, B3PW91, BH&HLYP, MPW1K, MPW1PW91, HCTH407 and PBE, on a number of relevant imines and ketones/aldehydes. Additionally, second-order Moller-Plesset perturbation theory was also evaluated. The results quantitatively reveal the manner in which the form of a method affects the calculated energy change and that there is substantial difference between results obtained with different methods even for structurally simple species. (C) 2010 Elsevier B.V. All rights reserved.