A mobile station apparatus that is adapted to communicate with a base station apparatus using a plurality of downlink component carriers, the mobile station apparatus comprising: a reception unit (203, 204, 205, 206, 207, 208, 209) adapted to receive, from the base station apparatus, a higher layer signal including first information used for indicating a first downlink component carrier, a decoding unit adapted to attempt to decode at least one physical downlink control channel on at least the first downlink component carrier; and a transmission unit (201, 202, 203, 204, 208, 209) adapted to transmit, to the base station apparatus, Hybrid Automatic Repeat Request, HARQ, control information using a first physical uplink control channel resource and a first physical uplink control channel format in a case that a physical downlink shared channel transmission on a second downlink component carrier different from the first downlink component carrier is indicated by a detection of the physical downlink control channel, wherein the transmission unit (201,202, 203, 204, 208, 209) is adapted to transmit, to the base station apparatus, HARQ control information using a second physical uplink control channel resource and a second physical uplink control channel format in a case that a physical downlink shared channel transmission only on the first downlink component carrier is indicated by a detection of the physical downlink control channel, the first physical uplink control channel format supports a number of information bits per subframe larger than a number of information bits per subframe supported by the second physical uplink control channel format, and the first physical uplink control channel format is used for transmitting the HARQ control information together with a scheduling request. a reception unit (203, 204, 205, 206, 207, 208, 209) adapted to receive, from the base station apparatus, a higher layer signal including first information used for indicating a first downlink component carrier, a decoding unit adapted to attempt to decode at least one physical downlink control channel on at least the first downlink component carrier; and a transmission unit (201, 202, 203, 204, 208, 209) adapted to transmit, to the base station apparatus, Hybrid Automatic Repeat Request, HARQ, control information using a first physical uplink control channel resource and a first physical uplink control channel format in a case that a physical downlink shared channel transmission on a second downlink component carrier different from the first downlink component carrier is indicated by a detection of the physical downlink control channel, wherein the transmission unit (201,202, 203, 204, 208, 209) is adapted to transmit, to the base station apparatus, HARQ control information using a second physical uplink control channel resource and a second physical uplink control channel format in a case that a physical downlink shared channel transmission only on the first downlink component carrier is indicated by a detection of the physical downlink control channel, the first physical uplink control channel format supports a number of information bits per subframe larger than a number of information bits per subframe supported by the second physical uplink control channel format, and the first physical uplink control channel format is used for transmitting the HARQ control information together with a scheduling request.