The effect of addition of anionic (sodium dodecyl sulfate, SDS) or cationic (cetyltrimethyl ammonium bromide, CTAB) surfactant on the hydrodynamic thickness of layers of unmodified (EHEC) and hydrophobically modified ethyl(hydroxyethyl)cellulose (HM-EHEC), adsorbed on anionic polystyrene latex particles (PSL), was studied by dynamic light scattering. The hydrodynamic layer thickness of EHEC increases in the presence of SDS or CTAB at low surfactant concentration due to the formation of polymer-surfactant clusters on the particle surfaces, followed by a reduction of this layer at higher levels of surfactant addition. The maximum in hydrodynamic thickness is observed at the critical aggregation concentration (cac) of the respective EHEC-surfactant complex, and the desorption is virtually complete around the critical micelle concentration of the pure surfactant. The interaction peak is more pronounced with SDS than in the presence of the cationic surfactant. For the HM-EHEC/SDS/PSL and HM-EHEC/CTAB/PSL systems, the hydrodynamic thickness decreased monotonically with increasing surfactant concentration, and the hydrodynamic radius of PSL does not pass through a maximum. The absence of an interaction peak for the adsorption of the hydrophobically modified polymer is attributed to a very low or nonexistent cac for the HM-EHEC-surfactant complexes. An increase or decrease in temperature for the EHEC/ SDS/PSL and HM EHEC/SDS/PSL systems had no noticeable effect on the maximum of the peak and other adsorption features.