Arising from the discussion about a sustainable development of the energy sector, more and more interest of different industrial branches (e.g. in the automotive field or by the energy supply companies) is actually directed to the use of fuel cells. They show high degrees of ef-ficiency, little pollution and the ability of combined heat and power generation, and moreover they are modularly built. As a fuel they need hydrogen, but the infrastructure of its supply is much worse than necessary. So, at least for a time of transition, hydrogen must be produced from hydrocarbon fuels. A new idea is the hydrogen production from liquid higher hydrocar-bon compositions, as diesel fuel, in a catalytic cracker. This diesel processor is based on a technology developed by the University of Essen-Duisburg at Duisburg. Liquid higher hydrocarbons, as diesel, also contain different sulfur compounds. The aim of this work was to gain knowledge about the influence of sulfur to a complete catalytic cracker system. The study consists of two parts, the first dealing with the influence of sulfur com-pounds to the catalytic cracker itself, and the second with the influence of the products of the reaction of sulfur compounds flowing with the resultant gas into the low-temperature Polymer Electrolyte Membrane Fuel Cell, PEMFC. In the catalytic cracker the influence of sulfur on the activity and the hydrogen selectivity of catalysts of two different precious metals used separately as well as in mixture is investi-gated. Furthermore, the catalysts stability under the cracking temperature of nearly 1,200 K is tested. As an example, the effect of sulfur-containing fuel to a PEMFC is shown and analysed. Moreover, a mathematical-physical model is developed, describing the effects of the degra-dation of a PEMFC by sulfur contamination. Finally, the efficiency of a desulfurizing unit, pre-connected to the fuel cell to extend its lifetime, is investigated.