In the case of a flat flexible support piece comprising an electrode arrangement, to which a high voltage can be supplied, for a dielectrically impeded plasma treatment of a surface to be treated, wherein the electrode arrangement has at least one flat electrode (3) and a dielectric layer (2) which has a support face for the surface to be treated and which is composed of flat flexible material and which electrically shields the at least one electrode (3) from the surface to be treated such that only a dielectrically impeded current flow between the at least one electrode (3) and the surface to be treated is possible when a plasma field is produced by the bias on the electrode (3) in a gas space between the electrode arrangement and the surface to be treated, simplified handling and increased safety are achieved in that the support piece has a high-voltage stage (14) for generating a high voltage, the output of said high-voltage stage being connected to the at least one electrode (3) by a connecting piece (17, 17′) on the support piece.