The metallization of organic thin films is a crucial point in the development of organic electronic devices. There is no method established yet to detect trace amounts of metal atoms in the organic thin films after metal deposition. Radiotracer measurements are probably the most sensitive tool to study diffusion and to quantify even very small amounts of material penetrating into the bulk. So far, this has been shown for metals and polymers, but not for thin ordered molecular organic films. Here, the first application of this technique on a well-characterized organic thin film system, diindenoperylene using thermally evaporated Ag containing 110mAg radiotracers is shown. The results show that Ag is mainly adsorbed on the surface, but indicate that already at moderate substrate temperatures small concentrations of Ag can penetrate into the organic thin films and agglomerate at the interface during metallization.