Data transmission and reception is provided by configuring control channels in a wireless communication system using a plurality of carriers. User equipment (UE) may monitor physical downlink control channel (PDCCH) candidates within common search spaces (CSSs) and User Equipment-specific search spaces (USSs). If the UE is configured with cross-carrier scheduling, when two PDCCH candidates originating from a CSS and a USS, respectively, have cyclic redundancy check (CRC) scrambled by the same Radio Network Temporary Identifier (RNTI) and have a common payload size and the same first control channel element (CCE) index, the UE may interpret that only the PDCCH originating from the CSS is transmitted, thereby solving ambiguity of downlink control information (DCI) detection.