Plasma treatment is often used to modify the surface properties of polymer films, since it offers numerous advantages over the conventional surface modification techniques. In this paper, a polypropylene (PP) film is plasma‐treated using a dielectric barrier discharge (DBD) operating in air at medium pressure (5.0 kPa). The modified polymer films are characterized using contact angle measurements, XPS‐analysis and attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy. Results show that plasma treatment leads to a remarkable decrease in contact angle owing to the implantation of oxygen‐containing functional groups. Using XPS and ATR‐FTIR, these oxygen‐containing groups can be identified as CO, CO and OCO. In this paper, it is also shown that XPS is well‐suited to provide quantitative chemical analysis of the PP films, while ATR‐FTIR can only give qualitative information. To perform quantitative ATR‐FTIR measurements, chemical derivatization will be explored in the near future. Copyright © 2008 John Wiley & Sons, Ltd.