The removal of adsorbed nitrogen from catalyst surfaces is one of the key processes in proceeding efficient catalytic treatments of nitrogen oxides in exhaust gases from automotive and stationary sources. This review summarizes the typical characteristics of three removal processes of surface-nitrogen on metal surfaces, i.e., (i) 2N(a) → Nz(g), (ii) N(a) + NO(a) → N₂O(a) → N₂(g) + O(a) and (iii) NO(a) + O(a) → NO₂(a) → NO₃^-(a) → N₂(g). In the first process desorbing N₂ is collimating along the surface normal direction and is vibrationally excited because a large amount of the binding energy is released in the associative process. N₂ in the second process collimates into a highly inclined direction on flat surfaces because N₂O lies on the surface immediately before dissociation. These characteristics are exemplified to be useful to examine the reaction pathway of NO_x decomposition on catalysts.