Surface modification of poly( aryl ether ether ketone) (PEEK) film surfaces by oxygen plasma treatment was investigated. Two procedures, the direct plasma treatment and the remote oxygen plasma treatment, were used as oxygen plasma treatments, and the efficiency of the hydrophilic modification was discussed. The direct and remote oxygen plasma treatments lead to degradation of the PEEK film as well as hydrophilic surface modification. The degradation disturbs the surface modification. The remote oxygen plasma treatment rather than the direct oxygen plasma is suitable for the hydrophilic surface modification of the PEEK film. The remote oxygen plasma treatment at 10 Wf or 60 s forms predominantly C-O groups rather than C=O groups as an oxygen-containing group on the PEEK surface and gives a highly hydrophilic surface with a contact angle of 44 degrees.