In contrast to most wet chemical synthesis routes, chemical vapor deposition (CVD) offers many degrees of freedom for the structuring of Pt nanoparticle catalyst systems, which is a prerequisite for the examination of structure-function correlations in heterogeneous catalysis. Two different suitable metal-organic Pt precursors [MeCpPtMe3 and novel PtMe2(iBu-COD)] were employed to generate highly defined, very narrowly distributed Pt nanoparticles with high active surface areas on well-specified TiO2 supports of differing surface properties. The TiO2 supports and the Pt nanoparticles were thoroughly characterized and tested in the water gas shift reaction. The influence of the support particle size and its surface chemistry (hydroxyl groups) as well as the nature of the metal-organic precursors used on the water gas shift (WGS) activity were investigated by nanotechnological methods within this study. A further modification of the support material was done by Na deposition. This catalyst was found to be a highly efficient WGS catalyst with an increase of the catalytic activity by a factor of 3 compared to the nonmodified system.