The correlation between surface tension parameters and the chemical composition of poly(amic acid) and polyimide films, before and after plasma treatment, was investigated. Calculations are based on the geometric mean approach according to Owens, Wendt, Rabel, and Kalble, on the Lifshitz-van der Waals acid/ base approach according to Van Oss, Good, and Chaudhury, as well as on the theoretical method which implies the quantitative structure-property relationships. The polar components for all films investigated contribute significantly to the total surface tensions, as due to the large electron-donor interactions. Plasma treatment alters the surface energy of samples, changing their surface polarity and wettability. Surface wettability and hydrophilicity trends for poly(amic acid)s and their polyimides were also studied by means of the free energy of hydration between compounds and water. These properties recommend the polyimides as excellent materials for electrical compounds and biomaterials.