An atmospheric pressure ambient air plasma technique is developed for technically simple treatment of inner and/or outer surfaces of plastic tubes and other hollow dielectric bodies. It is based on a specific type of surface dielectric barrier discharge generating visually diffuse plasma layers along the treated dielectric surfaces using water-solution electrodes. In the present study the technique is used for surface activation of PVC tubes. XPS analyses of treated surfaces are performed and the aging effect on the treated PVC surface is studied.