Sorption and transport of oxygen in dry and water saturated Kapton(R) polyimide films of different thickness were investigated at 25-degrees-C with pure oxygen using : (i) a manometric permeation apparatus (gas-membrane-gas configuration), (ii) a high pressure gas sorption equipment, and (iii) an electrochemical technique based on the oxygen Clark electrode (liquid-membrane-liquid configuration), respectively. A sharp increase of permeability, solubility, and diffusivity coefficient as thickness increased in the range 13-50 mum was observed for the oxygen transport through both dry and water-saturated Kapton. The variation of the oxygen transport parameters in the range of thicknesses investigated were small in the case of dry polyimide compared to the case of the water-saturated polymer. An interpretation is presented in which the oxygen transport parameters in both dry and water-saturated conditions are analyzed in terms of ’dual-sorption-dual-mobility’ model and related to the different polymer morphologies. such as crystallinity level, crystallinity orientation and excess free volume content, characterizing samples of different thickness.