The correlation between thermal aging effects of three-way catalysts (TWC) and their spatial temperature profiles and CO conversion was studied. The study is based on temperature profiles within fresh and aged catalysts, as well as CO concentrations at the outlet of the samples. The highest deactivation was always observed at the catalyst inlet area. The modelling approach with separated reaction mechanisms for palladium and rhodium used here assumes a direct correlation between the temperature profiles resulting from the exothermal chemical reactions and the catalytically active surface area. The noble metal dispersion is determined by low temperature CO chemisorption measurements. It is used in simulation as the relevant parameter for quantitative prediction of the catalyst performance.