A method for transmitting uplink control information by a user equipment (UE) configured with a plurality of cells including a primary cell and a secondary cell in a wireless communication system, the method includes identifying Hybrid Automatic Repeat reQuest-Acknowledgement (HARQ-ACK)(0), HARQ-ACK(1), HARQ-ACK(2) and HARQ-ACK(3); and transmitting bits b(0)b(1) using a Physical Uplink Control Channel (PUCCH) resource based on the HARQ-ACK(0), the HARQ-ACK(1), the HARQ-ACK(2) and the HARQ-ACK(3), where the HARQ-ACK(0) and the HARQ-ACK(1) indicate ACK/NACK/DTX responses to data blocks related to the primary cell, the HARQ-ACK(2) and the HARQ-ACK(3) indicate ACK/NACK/DTX responses to data blocks related to the secondary cell, and n(1)PUCCH,0 indicates a PUCCH resource linked to a PDCCH (Physical Downlink Control Channel) on the primary cell.