The structure and dynamics of the nonionic surfactant C12E5 adsorbed from aqueous solution to the inner pore walls of two types of CPG porous silica glass (pore diameters 35 nm (CPG-240) and 13 nm (CPG-75)) have been investigated with H-2 NMR. Broad Lorentzian shape peaks, instead of a Pake pattern, were observed, which imply the averaging of the anisotropic quadrupole interaction by isotropic motions inside the samples. The spin-spin relaxation rate R-2 is 3 kHz, corresponding to motions of a correlation time of 3.8 mus, in both porous materials. Information about the aggregate curvature is derived from a relative order parameter, S-rel, for three positions of the H-2 label along the alkyl chain. S-rel values in a range from 1.0 to 1.1 are found for all label positions and both glass samples, which suggests a flat bilayer structure of the surface aggregates. Lateral diffusion of surfactants along the pore wall is discussed as the dominant motional mode determining the relaxation rates. Diffusion coefficients along the pore walls are estimated to 1 x 10(-11) m(2)/s and 7 x 10(-13) m(2)/s for CPG-240 and CPG-75, respectively, based on a simple model. Both values are below the corresponding values in free surfactant layers, viz., D = 3 x 10(-11) m(2)/s. These facts suggest that the lateral diffusion of the surfactant on the pore wall of CPG-240 is decreased due to the interaction with the silica surface, and the much stronger decrease on the pore wall of CPG-75 is mainly due to the confined geometry as the pore size is approaching the thickness of the surfactant bilayer. The proposed distinction between the effects of surface interactions and of geometrical confinement on the diffusional motion of the surfactant is supported by a comparison of surfactant adsorbed layers on concave and convex surfaces.