a variable cam timing phaser for an internal combustion engine having a concentric camshaft can include a stator having an axis of rotation . an outer rotor can rotate independently relative to the axis of rotation of the stator . a combination of an outer vane and cavity can be associated with the outer rotor to define first and second outer variable volume working chambers . a radially inner located rotor can rotate relative to the axis of rotation and independently of both the stator and the outer rotor . a combination of an inner vane and a cavity can be associated with the inner rotor to define first and second inner variable volume working chambers . when the first and second , outer and inner chambers selectively communicate with a source of pressurized fluid , phase orientation of the outer and inner rotors with respect to one another and with respect to the stator is facilitated .