In order to decrease their hydrophobicity and thus to reduce nonspecific protein adsorption, macroporous polystyrene-divinylbenzene (PS-DVB) particles have been coated with dextran. To favor its adsorption, the polysaccharide was previously substituted with low concentrations of phenoxy groups. Different hydrophobically modified dextrans, labeled with 4-amino-TEMPO, were allowed to adsorb onto PS-DVB, and the conformation of polymer chains in the deposited layer was studied by EPR spectroscopy. For a given polymer, it was found that the mobility of chains increases with the surface coverage. Conversely, the stiffness of the adsorbed layer was shown to increase with the phenoxy group content of dextran. Furthermore, results of EPR experiments carried out in the presence of bovine serum albumin (BSA) were in good agreement with measured nonspecific BSA adsorption and were of significance in interpreting the interaction mechanism between proteins and dextran-modified polystyrenes.