A method for producing acrolein and/or acrylic acid from propane, whereby the propane undergoes partial homogeneous and/or heterogeneous catalysed oxydehydrogenation with molecular oxygen in a first reaction step to form propane. The product gas mixture formed in the first reaction step is subsequently used to produce acrolein and/or acrylic acid by means of gas-phase catalytic propane oxidation. The method is characterised in that the molecular oxygen which is required in the first reaction step and is different from the recycled oxygen gas is added to the initial reaction gas mixture of the first reaction step as modified air containing nitrogen with the proviso that the nitrogen content of the modified air is lower than and the oxygen content of the modified air is greater than the corresponding air contents. The invention is also characterised in that at least one part of the molecular nitrogen contained in the product gas mixture is separated from the product gas mixture before the product gas mixture containing propane formed in the first reaction step is further processed to produce acrolein and/or acrylic acid in at least one additional reaction step.