A method for improving radio resources, a method for transmitting a status report, and a receiving apparatus (receiver) in a mobile communication system are disclosed. In transmitting a status report by a receiving side RLC, although data that has not been received (missing PDU) is discovered, the receiving side does not immediately request its retransmission but transmits the status report after the lapse of a certain time (namely, a time point at which a timer expires), to thus reduce radio resources consumed for transmission of the status report.