Atmospheric pressure plasma discharges are often used to modify surfaces of polymer films due to their excellent ability to be integrated in the manufacturing line. The plasma treatment leads to surface activation and is employed to improve printability or adhesion. These effects are well known, however there is a necessity for a process control to prove the efficiency and the homogeneity of the modification, and furthermore to have a method to ensure quality requirements or for the description of the complex modification processes. In this study, optical emission spectroscopy was utilized to investigate the plasma of a dielectric barrier discharge used for treating polyethylene films. The aim was to find correlations between both the influences of plasma parameters as well as the reactions in the plasma and the resulting surface properties. The surface modifications were analyzed by contact angle measurements and X-ray photoelectron spectroscopy (XPS). (C) Koninklijke Brill NV, Leiden, 2011