The catalytic partial oxidation (CPOX) of ethanol-blended fuels is studied over rhodium/alumina coated monoliths with ethanol/iso-octane mixtures as model systems. Blends containing 5-85 vol.% ethanol are investigated, as well as the pure substances. All mixtures show a hydrogen yield of over 80% in millisecond contact times, with the highest yield for a blend with 10 vol.% ethanol. For a high ethanol concentration in the blend, generally a high by-product formation is observed already at fuel lean conditions. The product yields cannot be linearly interpolated from the yields of the pure substances. In addition, the commercial fuels 95 RON gasoline and E85 are studied, revealing similar product yields in CPOX of the commercial fuels and the corresponding ethanol/iso-octane blends. Thus, two-component mixtures can be proposed as model system for the complex compositions of commercial fuel. (C) 2012 Elsevier B.V. All rights reserved.