The review presents a concise discussion of reports on hydrogenation of N-containing heteroaromatic compounds in relation to the hydrodenitrogenation process (HDN), along with hydrogenation mechanisms of the most representative examples of the compounds studied. The influence of electronic properties of aromatic structures, with the special emphasis on the resonance stabilization energies and the interatomic C-C and C-N distances, on the susceptibility for their hydrogenation has been considered. The importance of an initial mode of substrate coordination in relation to the reaction products formed is underlined.