A method for transmitting uplink control information by a communication apparatus configured with a plurality of cells including a primary cell and a secondary cell in a wireless communication system is discussed. The method includes identifying Hybrid Automatic Repeat reQuest—Acknowledgement (HARQ-ACK) information indicating Acknowledgement/Negative Acknowledgement/Discontinuous Transmission (ACK/NACK/DTX) responses to data blocks related to the primary cell and to the secondary cell; selecting a Physical Uplink Control Channel (PUCCH) resource depending on the HARQ-ACK information; and transmitting the HARQ-ACK information through a constellation point on the selected PUCCH resource, wherein when the HARQ-ACK information indicates a NACK/DTX response to each data block related to the secondary cell, the selected PUCCH resource is a PUCCH resource linked to a Physical Downlink Control Channel (PDCCH) on the primary cell.