Vertical fluxes of participate organic carbon (POC) from the euphotic zone to the deep sea are an important part of the carbon cycle in the oceans. In this study, oceanic fluxes of POC below the euphotic zone were simulated with the Hamburg ocean carbon cycle model (HAMOCC5.1) by using different POC-flux parameterizations and compared with sediment trap data. Overall, the geochemical distributions in the deep sea showed a high sensitivity to the selection of POC flux parameterization. Below 2000 m in the oceans, differences between simulated and observed carbon tracers (PO4, Alk*) and model-data differences of POC fluxes are lowest when a regionally variable POC flux parameterization is used. Specifically, model-data differences are lowest in the subtropics when simulated vertical POC flux considers mineral ballasting, while they are lowest in the Arabian Sea and west coast of Africa when a mineral dust parameterization is used for the vertical POC flux. Copyright 2006 by the American Geophysical Union.