Aspects in mathematical modelling of the catalyst section of an hybrid combustor for gas turbine applications are addressed. First, the identification of the simplest model accounting with reasonable accuracy for all the phenomena occurring in the combustor is investigated by comparing simulation results of mathematical models with different extent of detail. Then selected applications are reported in order to show how mathematical models can be used not only for classical scale-up and design purposes, but also as interactive tools during experimental research work in the development of catalytic combustor technology. The roles of surface area and specific activity, the effect of pressure in pilot scale experiments and the scale up of laboratory data are discussed in this respect.