The invention relates to a monitoring system for monitoring CPR performance and a reference unit for use in the system. The system comprises a measuring unit for positioning on the chest of a patient or manikin monitoring the movements applied to the chest, wherein the system also comprises a reference unit, the reference unit comprising sensors for measuring the movements thereof, wherein said units comprises means for wireless communication, one of the units comprising a signal analyzing means and a signal receiver coupled thereto for receiving said wireless communication, and the other unit comprising a signal transmitter for transmitting the measured signals to the signal receiver.
