Polydimethylsiloxane sheets were used to determine freely dissolved concentrations (C<inf>diss</inf>) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the Belgian coastal zone. Equilibrium models were used to predict the whole water concentrations (C<inf>ww</inf>) of these compounds as well as their concentrations in sediment, suspended particulate matter (SPM) and biota. In general, contaminant concentrations were predicted well for whole water and biota. C<inf>ww</inf> was increasingly underpredicted as K<inf>oc</inf> increased, possibly because of the presence of black carbon. Concentrations in biota were overestimated by the equilibrium approach when logK<inf>ow</inf> exceeded 6.5, suggesting an increasing role of transformation processes. Concentrations of PAHs and PCBs in sediment and SPM were consistently underpredicted although a good correlation between measured and predicted values was observed. This was potentially due to the use of experimental K<inf>oc</inf> values which have been found to underestimate partitioning of hydrophobic substances to sediment in field studies.