X-ray photoelectron spectroscopy was used to determine the influence of liquid phase oxidation on the surface structure of coals. The surface composition changes (increase in sulfur and carbon content and decrease in mineral matter amount), together with the content ratio of N/C, prove the applicability of the two-component model to describe the structure of coal. The mobile phase contains sulfur but no nitrogen compounds. Analysis of the C 1s peak shape enabled detailed discussion of the formation of oxygen-containing surface groups, depending on the starting coal rank and concentration and type of the oxidizing solution.