A radio communication terminal comprising: a receiving section that receives, via an enhanced physical downlink control channel, referred to as E-PDCCH, a control signal including an ACK/NACK indicator, the E-PDCCH being a channel that is frequency-multiplexed with a physical downlink data channel, referred to as PDSCH; a control section that determines, based on the ACK/NACK indicator, whether to transmit an ACK/NACK signal for downlink data using a first dynamic ACK/NACK resource dynamically allocated or using a specific resource specified beforehand, the first dynamic ACK/NACK resource being a resource associated with an index of an enhanced control channel element, referred to as eCCE, to which the control signal of the E-PDCCH is assigned in a first dynamic ACK/NACK region provided in an uplink channel; and a transmitting section that transmits the ACK/NACK signal using the determined first dynamic ACK/NACK resource or said specific resource based on the determination performed by said control section, characterized in that the first dynamic ACK/NACK region is overlapped with a second dynamic ACK/NACK region including second dynamic ACK/NACK resources that are resources associated with an index of a control channel element, referred to as CCE, to which a control signal of a physical downlink control channel, referred to as PDCCH, is assigned, the PDCCH being a channel that is time-multiplexed with the PDSCH; the ACK/NACK indicator instructs the radio communication terminal to use the specific resource when the first dynamic ACK/NACK resource associated with the index of the eCCE to which the control signal for the radio communication terminal is assigned collides with the second dynamic ACK/NACK resource associated with the index of the CCE to which the control signal for another radio communication terminal is assigned. a receiving section that receives, via an enhanced physical downlink control channel, referred to as E-PDCCH, a control signal including an ACK/NACK indicator, the E-PDCCH being a channel that is frequency-multiplexed with a physical downlink data channel, referred to as PDSCH; a control section that determines, based on the ACK/NACK indicator, whether to transmit an ACK/NACK signal for downlink data using a first dynamic ACK/NACK resource dynamically allocated or using a specific resource specified beforehand, the first dynamic ACK/NACK resource being a resource associated with an index of an enhanced control channel element, referred to as eCCE, to which the control signal of the E-PDCCH is assigned in a first dynamic ACK/NACK region provided in an uplink channel; and a transmitting section that transmits the ACK/NACK signal using the determined first dynamic ACK/NACK resource or said specific resource based on the determination performed by said control section, the first dynamic ACK/NACK region is overlapped with a second dynamic ACK/NACK region including second dynamic ACK/NACK resources that are resources associated with an index of a control channel element, referred to as CCE, to which a control signal of a physical downlink control channel, referred to as PDCCH, is assigned, the PDCCH being a channel that is time-multiplexed with the PDSCH; the ACK/NACK indicator instructs the radio communication terminal to use the specific resource when the first dynamic ACK/NACK resource associated with the index of the eCCE to which the control signal for the radio communication terminal is assigned collides with the second dynamic ACK/NACK resource associated with the index of the CCE to which the control signal for another radio communication terminal is assigned.