A method for operating a relay station in a wireless communication system includes: obtaining information regarding assigned subframes among a plurality of subframes; monitoring a PDCCH (Physical Downlink Control Channel) carrying information regarding a radio resource allocation within the assigned subframes; and receiving data from a base station on the basis of the radio resource allocation of the monitored PDCCH. The relay station may operate to guarantee compatibility with an existing terminal in a wireless communication system. Also, a method for assigning radio resources between a base station and the relay station is defined.