In this paper, we will propose a Cooperative Power and Contention control MAC (CPC-MAC) protocol in Cognitive Radio Ad Hoc Networks to solve the multichannel hidden terminal Primary User (PU) problem by build appropriate number of monitor nodes in suitable positions. There are two functions in this mechanism. First, secondary user (SU) transmitter sends the RTS frame including transmission power to SU receiver, SU receiver sends CTS frame including receiving power to SU sender. Monitor nodes send position and receiving power to SU sender and SU receiver. SU transmitter selects three monitors that their receiving powers are approach to each other. SU transmitter estimates its position and sending power by deterministic propagation model. This will reduce the interference to hidden PU terminal. Second, the SU in the transmission range of the PU will send one highest priority interrupt frame in control channel to one-hop SU neighbors to protect the PU. We also compare our proposed scheme to the existing IEEE 802.11 DCF and the other MAC protocols in Cognitive Radio ad hoc networks using ns2 simulation tool. We will show that CPC-MAC will improve the system throughput and reduce the energy consumption.