RF plasma of CF4/CH4 (> 5) was subject to further investigation by XPS and the contact angle method. An attempt has been made aiming at distinguishing the mechanistic aspects of PET surfaces exposed to CF4/CH4 plasmas. It follows that in addition to region 3 (83.3-0.0% CF4) there are two regions within the range of 83.3-100% CF4. Region 1 (100-96.8% CF4) is a region of etching/fluorination predominated and region 2 (96.8-83.3% CF4) is polymerization predominated. For a complete description of the entire process the fluorination (or grafting, implantation) should be incorporated into the CAP model. The homogeneity along depth of the surface layers can be intuitively observed with the help of the angle-dependent XPS, which turns out to be of great importance in comparison with the sampling depth of the contact angle technique under various experimental conditions.