Methods and apparatus for selectively heating a target tissue via radiofrequency (RF) electrical energy. Apparatus of the invention includes an electrode unit having a plurality of concentric electrodes, wherein supply of electrical energy to each electrode may be independently controlled such that each of the plurality of electrodes has a different value of an electrical parameter for tissue treatment. Methods for selectively heating and treating tissue, for detecting thickness of tissue, and for determining a treatment value of an electrical parameter for each of a plurality of electrodes of an electrode unit are also disclosed.