Hydrodynamic layer thicknesses of adsorbed polyethylene oxides (PEO), polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO) block copolymers, and polyvinyl alcohols (PVA) of different molar mass and composition are determined by photon correlation spectrometry (PCS) and ultracentrifugation (UC). The adsorbents used are precipitated silica and polystyrene latex. The increase of the diffusion coefficient, D, of the bare silica particles with reduction of the electrostatic double layer is related to the existence of immobilized water near the charged interface. At high PEO adlayer thicknesses no influence of the extension of the double layer exists. PCS allows precise determination of the critical flocculation concentration (c.f.c.). An influence of the particle curvature on the hydrodynamic adlayer thicknesses is to be seen. The conformation of adsorbed polymer is determined by the surface-polymer interaction; hydrogen bonds on the polar silica surface and hydrophobic interactions on the apolar latex surface are decisive.