Molecular simulations have been carried out on aqueous electrolytes in cylindrical pores a few nanometers in diameter, with uncharged wall or with dispersed, discrete charges modeling silica. The results show a classical Stern layer of adsorbed counterions near the wall, and then a diffuse layer with depleted ion concentration in the interfacial region. The depletion region coincides roughly with the more ordered water structure in the interface. Examination of the interaction energy shows that hydration energy of the ions disfavors the interior, suggesting the importance of the solvent structure near the wall. Comparison with the linearized Poisson-Boltzmann theory indicates qualitative differences in the predicted interfacial behavior.