Abstract: The invention is directed to a cryosurgical instrument and to an accessory system operating on the base of refrigerant evaporation, wherein the portions of the refrigerant are periodically provided to the distal cryotip of the cryosurgical instrument via a central lumen thereof. The internal surface of the distal cryotip is preferably covered by a porous coating capable of soaking at least one portion of the refrigerant. The vapors obtained as a result of the refrigerant boiling on the porous coating of the cryotip are preferably removed through the central lumen of the cryosurgical instrument into the atmosphere. These features may be combined to construct a cryosurgical instrument with relatively high freezing power and small outer diameter which may be designed as a flexible cryocatheter or alternatively as a rigid cryoprobe.