The present invention relates to a wireless communication system. In particular, the present invention relates to a method for handling physical downlink control channels (PDCCHs) in a user equipment, the method comprising: receiving a plurality of control channel elements (CCEs) from a base station; performing blind decoding of the plurality of CCEs in CCE aggregation units; and identifying a CCE aggregation level used for the PDCCH transmission, on the basis of the blinding decoding result, wherein the CCE aggregation level is relevant resource mapping of the control information included in the PDCCH.