To provide a mobile terminal apparatus, radio base station apparatus and radio communication method for enabling data signals and control information for a plurality of component carriers to be transmitted efficiently, a radio communication method of the invention is characterized in that a mobile terminal apparatus maps a retransmission response signal and another signal to different resources in a first mode for transmitting a retransmission response signal for each downlink CC of a plurality of downlink CCs, while mapping the retransmission response signal and another signal to the same resources in a second mode for transmitting a single retransmission response signal for a plurality of downlink CCs, and that the radio base station apparatus receives the uplink signal, preforms resource-demapping on each of the retransmission response signal and another signal mapped to different resources in the first mode, while performing resource-demapping on the retransmission response signal and another signal mapped to the same resources in the second mode, and demodulates the retransmission response signal.