Chemithermomechanical pulp has been treated by cold plasma of oxygen, nitrogen, argon or air. The wettability increases as a result of treatment by oxygen or air plasmas but decreases when argon or nitrogen plasmas are used. The initial water absorption rate can be improved by more than 100 % using an oxygen plasma. After subsequent ageing of the pulp the improvement was ca 200 %. Electron Spectroscopy for Chemical Analysis (ESCA) shows that the oxygen plasma treatment increases the oxygen content of the fibre surfaces due to oxidation and/or removal of fatty acids, resin acids, and probably also lignin. The amount of extractable material increases after the plasma treatment, probably due to oxidation and scission of the lignin and the carbohydrates. This oxidized low molecular weight material may act as a surfactant decreasing the surface tension of the absorbing liquid and thus enhance the absorption rate.