A cam phaser including a rotation phaser and a hydraulic valve hydraulically loading the rotation phaser, wherein the hydraulic valve is connectable torque proof with a cam shaft so that the cam shaft is rotatable, wherein the rotation phaser includes a stator and a rotor configured coaxial with the stator, wherein the rotor is rotatable relative to the stator, wherein the hydraulic valve is configured so that it protrudes at least partially into the rotation phaser, wherein an adapter is provided for a relative axial positioning of the rotor and the stator. According to the invention the adapter is configured for loose mounting in the rotation phaser so that a fixated connection of the adapter in the rotation phaser is provided when the cam shaft is mounted at the hydraulic valve.