The invention relates to an active accessory for applying diathermy by radio frequency, applied by contact electrodes in the body cavities, which comprises: a grip (1); an intermediate stem (2); a distal area (3); at least one insulated active electrode (31), arranged in the distal area (3); and a cable (4) for connecting to a radio frequency current generator. The grip (1) has a shaped member (11) that can be felt by touch when holding the grip (1), arranged conveniently to provide a reference indicating the position of the electrode (31), each electrode of the accessory being made up of a metal electrode insulated by a ceramic, plastic or resin coating, with a thickness of 20 to 500 micrometres. In the embodiment, the intermediate stem (2) has an electrode (21) for supplying radio frequency current.