Disclosed is a radio (wireless) communication system providing a radio communication service and a terminal, and more particularly, to a method for retransmitting protocol data unit upon receiving a HARQ delivery failure notification with respect to a particular RLC data PDU by a RLC, only if the RLC did not receive a positive response (i.e., ACK) with respect to the particular RLC data PDU from a previous RLC status PDU within an Evolved Universal Mobile Telecommunications System (E-UMTS) that has evolved from a Universal Mobile Telecommunications System (UMTS) or a Long Term Evolution (LTE) system.