Two activated carbons from different sources were oxidized with nitric acid and hydrogen peroxide and the effects of this on their porous structure and sorption of water and methanol were studied. The microstructural properties were derived from analysis of N2 isotherms. The surface acidity was assessed using Boehm titration and potentiometric titration. Changes in the surface chemistry were also monitored using difference reflectance IR Fourier transform. From the potentiometric titration the pKa distributions were calculated and the surface density of acidic groups was evaluated. The structural and surface chemical results demonstrate that carbons derived from different sources can have wide variation in their oxidation susceptibility. To further evaluate the impact of the recorded changes due to oxidation in the carbons studied, sorption uptake of water and methanol was measured and correlated with the acidity of the carbon surfaces.