A camshaft phaser for use with an internal combustion engine for controllably varying the phase relationship between a crankshaft and a camshaft in said internal combustion engine, said camshaft phaser comprising: an input member connectable to said crankshaft of said internal combustion engine to provide a fixed ratio of rotation between said input member and said crankshaft; an output member connectable to said camshaft of said internal combustion engine and defining an advance chamber and a retard chamber with said input member; a valve spool coaxially disposed within said output member such that said valve spool is rotatable relative to said output member and said input member, said valve spool defining a supply chamber and a vent chamber with said output member; and an actuator which rotates said valve spool in order to change the position of said output member relative to said input member by 1) supplying pressurized oil from said supply chamber to said advance chamber and venting oil from said retard chamber to said vent chamber when retarding the phase relationship of said camshaft relative to said crankshaft is desired and 2) supplying pressurized oil from said supply chamber to said retard chamber and venting oil from said advance chamber to said vent chamber when advancing the phase relationship between said camshaft relative to said crankshaft is desired, wherein:said input member is a stator having a plurality of lobes; said output member is a rotor coaxially disposed within said stator, said rotor having a plurality of vanes interspersed with said lobes; said advance chamber is one of a plurality of advance chambers defined by said plurality of vanes and said plurality of lobes; and said retard chamber is one of a plurality of retard chambers defined by said plurality of vanes and said plurality of lobes, wherein said supply chamber is one of a plurality of supply chambers defined with said rotor and said vent chamber is one of a plurality of vent chambers defined with said rotor such that said plurality of supply chambers are arranged in an alternating pattern with said plurality of vent chambers, wherein said rotor includes a rotor central hub from which said plurality of vanes extend radially outward therefrom, said rotor central hub having a rotor central through bore extending axially therethrough, characterized in that said rotor central hub defines an annular valve spool recess coaxially therein such that said annular valve spool recess divides said rotor central hub into a rotor central hub inner portion and a rotor central hub outer portion; and said valve spool is rotatably located coaxially within said annular valve spool recess. an input member connectable to said crankshaft of said internal combustion engine to provide a fixed ratio of rotation between said input member and said crankshaft; an output member connectable to said camshaft of said internal combustion engine and defining an advance chamber and a retard chamber with said input member; a valve spool coaxially disposed within said output member such that said valve spool is rotatable relative to said output member and said input member, said valve spool defining a supply chamber and a vent chamber with said output member; and an actuator which rotates said valve spool in order to change the position of said output member relative to said input member by 1) supplying pressurized oil from said supply chamber to said advance chamber and venting oil from said retard chamber to said vent chamber when retarding the phase relationship of said camshaft relative to said crankshaft is desired and 2) supplying pressurized oil from said supply chamber to said retard chamber and venting oil from said advance chamber to said vent chamber when advancing the phase relationship between said camshaft relative to said crankshaft is desired, wherein:said input member is a stator having a plurality of lobes; said output member is a rotor coaxially disposed within said stator, said rotor having a plurality of vanes interspersed with said lobes; said advance chamber is one of a plurality of advance chambers defined by said plurality of vanes and said plurality of lobes; and said retard chamber is one of a plurality of retard chambers defined by said plurality of vanes and said plurality of lobes, wherein said supply chamber is one of a plurality of supply chambers defined with said rotor and said vent chamber is one of a plurality of vent chambers defined with said rotor such that said plurality of supply chambers are arranged in an alternating pattern with said plurality of vent chambers, wherein said rotor includes a rotor central hub from which said plurality of vanes extend radially outward therefrom, said rotor central hub having a rotor central through bore extending axially therethrough, characterized in that said rotor central hub defines an annular valve spool recess coaxially therein such that said annular valve spool recess divides said rotor central hub into a rotor central hub inner portion and a rotor central hub outer portion; and said valve spool is rotatably located coaxially within said annular valve spool recess.