A method for receiving a physical downlink control channel (PDCCH) by a user equipment (UE) in a wireless communication system, the method comprising: monitoring, in a common search space and one or more UE-specific search spaces on a primary component carrier, PDCCH candidates having a same radio network temporary identifier (RNTI), a same payload size and a same first control channel element (CCE) index but different set of control information fields; and receiving, in the common search space on the primary component carrier, the PDCCH if the UE is configured with a carrier indicator field.