An N-methyl-substituted triacetonamine compound is prepared by reacting at least one triacetonamine compound (I) with formaldehyde under reductive conditions, in the presence of hydrogen and in the presence of a supported catalyst, wherein the supported catalyst contains at least one metal M, wherein the metal M is selected from the group consisting of V, Cr, Mo, Mn, Ni, Pd, Pt, Fe, Ru, Os, Co, Rh, Ir, and Cu.