An electrosurgical instrument includes an instrument shaft, a suction tube extending along the shaft, and a tissue treatment electrode at the distal end of the shaft. The tissue treatment electrode includes at least a first part and a second part, the first and second parts each having an outer section including mating surfaces adapted to form a close-fitting barrier when the first and second parts are mated one with another, such as to inhibit the passage of gas across the barrier. At least one of the parts also includes an inner section with a longitudinal recess so as to form a suction lumen when the first and second parts are mated one with another. The suction lumen is in fluid communication with the suction tube, the tissue treatment electrode also including one or more apertures in communication with the suction lumen.
