IEEE802.11DCF employs RTS/CTS (Request To Send/Clear To Send) mechanism for mitigating effect of hidden terminals. The RTS/CTS mechanism sets transmission deferral timer to neighbor terminals by exchanging RTS and CTS between transmitter and receiver. Then, in the case that RTS/CTS exchange succeeds, effect of hidden terminals could be suppressed, otherwise, any neighbor which received RTS and/or CTS defers its new transmission needlessly although DATA packet corresponding to the previous RTS/CTS exchange will not be transmitted. In this paper, we propose Cancel CTS, procedure in order to cope with the unnecessarily transmission deferment. Results of computer simulation confirms that our method well improves the throughput performance of IEEE802.11DCF.