Perovskite-like mixed oxides La(0.9)A(0.1)A＇BO3+delta (A＇=Ce or Eu; B=Mn or Co) and La0.8Sr0.2BO3+delta (B=Mn, Fe, Co or Ni) prepared by the amorphous citrate method were used as catalysts for NO reduction by hydrogen. XRD patterns showed a fully crystalline perovskitic structure only in the case of Ce-and Eu-substituted samples. The results suggest that the presence of structural defects is important for the activity of these catalysts, as shown by pretreatment under different atmospheres (He and O-2) La0.9Ce0.1CoO3+delta was the most active of the mixed oxide catalysts investigated and its activity was influenced by the presence of both anion vacancies and Co2+ species. La0.8Sr0.2NiO3+delta showed a particular catalytic behaviour, attributed to surface Ni reduction.