A synergetic effect in the catalytic activity has been found after palladium introduction in Mn-Al-O systems. The magnitude of the synergetic effect depends on the types of the oxidic manganese species: oxide Mn3O4, spinel (Mn, Mg)[Mn, Al](2)O-4 or hexaaluminate (Mn, Mg)LaAl11O19. The synergetic effect of Pd and manganese-containing compounds is observed only if palladium is introduced to the low-temperature precursor of the manganese alumina spinet or manganese hexaaluminate. The synergetic effect is not observed when high-temperature samples with formed spinet or hexaaluminate phases are modified with Pd. (c) 2006 Elsevier B.V. All rights reserved.