Surface treatment of polymer films is usually necessary to improve surface wetting and adhesion characteristics. Traditional liq. chem. processes have several disadvantages in contrast to dry finishing processes, like plasma technol. Dielec. barrier discharges at atm. pressure are extensively studied for surface treatment, however, almost no research has been done on surface treatment with a dielec. barrier discharge at medium pressure. Therefore, in this paper, a polypropylene (PP) film is plasma-treated with a dielec. barrier discharge (DBD) in nitrogen at medium pressure (5.0 kPa). The surface properties of the plasma-treated samples are examd. using contact angle measurements, XPS and at. force microscopy (AFM). Results show that the surface wettability is significantly enhanced after plasma treatment. The incorporation of nitrogen on the surface is significant (10 at%), demonstrating the ability of the used DBD set-up to generate nitrogen-contg. functional groups on the PP surface. Nevertheless, a considerable amt. of oxygen (10 at%) is incorporated onto the PP surface underlining the extreme reactivity of oxygen active species and the difficulty in overcoming the air contamination problem. Moreover, AFM anal. reveals that the nitrogen plasma creates large changes in the surface morphol. of the PP film due to the selective etching of the amorphous regions of the polymer film.