High density polyethylene (HDPE) is often used industrial polymer because of its good mechanical properties as high flexibility and tensile strength, high chemical resistance, easy processing and low price. Low surface energy of HDPE causes its low adhesion to printings, coatings and adhesives, what limits its industrial use. The aim of this work is to improve wettability of HDPE surface while bulk properties are kept. Atmospheric Diffuse Coplanar Surface Barrier Discharge (DCSBD) operated at frequency 50 kHz in ambient air was used. The main advantages of this plasma source are possibility to operate it at atmospheric pressure, high power density and good its good applicability in-line processes. Surface properties of samples were analyzed via sessile drop contact angle measurement and calculation of surface energy and its gamma(AB) and gamma(LW) components using Owens, Wendt, Rabel and Kaelble model (OWRK). Exposure time was 1.5 - 20 s and distance between samples and electrode was 0.1, 0.2 or 0.3 mm. Obtained results show that the surface energy of treated HDPE depends not only on exposition time but also on distance between the sample and the electrode. The best results were obtained for 10 sec treatment at the lowest distance between sample and electrode. Surface energy increased up to 72 mJ/m(2) compared with 38 mJ/m(2) of untreated HDPE. Aging tests proved only weak decrease in surface energy during first 720 min after the plasma treatment.