Adsorption of poly(ethylene oxide) within porous glass, from aqueous solutions, was investigated as a function of the polymer molecular weight, pore diameter, concentration, and time, using differential refractometry. The kinetics of the process was found to depend on the ratio of pore diameter to the correlation length in the polymer solutions. The adsorbed amount exhibited a dependence on pore diameter for the longer molecular weights, with an unexpected observation of a higher adsorption in smaller pores. This observation is explained by the interplay between geometry-dependent enthalpic gain due to adsorption and entropic loss due to confinement.