A method and apparatus are provided for reducing excessive retransmission delays which may occur due to the loss of the last packet of a transmission buffer in a Radio Link Control (RLC) layer of a mobile communication system. The method includes receiving a Service Data Unit (SDU) from a higher layer, dividing the SDU into a plurality of Packet Data Units (PDUs), and storing the PDUs in a buffer, setting a poll bit for a last PDU from among the PDUs stored in the buffer, the poll bit requesting a status report, and repeatedly transmitting the last PDU having the setup poll bit at least twice from a sender to a receiver, regardless of whether there is a request for retransmission of the last PDU.