The Baltic Sea is optically a multi-componental water and has exceedingly high levels of colored dissolved organic matter (CDOM, also referred as yellow matter, gilvin or gelbstoff). CDOM is a complex mixture of chemical bonds originating from the decay of photosynthetically produced organic matter. It influences the aquatic light field substantially. A quantitative description of the dynamics and variability is often required to predict accurately light penetration and hereafter e.g. primary production. The present study is a first attempt to include CDOM into a Baltic Sea model. The model integrations are based on a fixed concentration in the 30 major rivers. In the absence of comprehensive measurements, a river inflow proportional to total organic carbon is assumed. Since origin and fate are still a matter of discussion, we test various decay rates of CDOM and compare the results with satellite observations. Best results are obtained when assuming a light dependent decay, compared to a temperature or time dependent decay. Treating CDOM as a conservative tracer does not lead to satisfactory results.