Commercial polymers in thin film form were used for modification by atmospheric RF plasma. The influence of the plasma treatments using Ar and Ar+O-2 on surface energy, morphology and chemical structure of the films was investigated. It was revealed that both modifications caused surface activation of the polymer film, but they obeyed different mechanisms enhancing polymer wettability. First, surface graphitization due to argon sputtering caused hydrogen to free the surface and then reacts with oxygen in the air. Second, surface oxidation is connected with the functional group formation. The reactions of Ti with the polymer led to the simultaneous formation of TiCl2, TiC, Ti-oxide and they contributed to film adhesion. In comparison with Ar, the mixed Ar+O-2 RF plasma treatment was a more timesaving process and had more influences on surface activation and film adhesion. (C) 2003 Elsevier B.V. All rights reserved.