The invention relates to a catalyst for removing nitrogen oxides from the exhaust gas of diesel engines, and to a method for reducing nitrogen oxides in the exhaust gas of diesel engines. The catalyst is made of a support body having a length L and a catalytically active coating that can consist in turn of one or more material zones. The material zones contain SCR catalytically active mixed oxides, comprising ceroxide, zirconium oxide, rare earth sesquioxide, and niobium oxide, and optionally tungsten oxide. The material zones further contain at least one compound selected from the group consisting of barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide, strontium carbonate, praseodymium oxide, lanthanum oxide, magnesium oxide, magnesium/aluminum mixed oxide, alkali metal oxide, alkali metal hydroxide, alkali metal carbonate, and mixtures thereof. Noble metal can also optionally be present in the catalyst.