Provided is a method for allocating radio resources in a mobile telecommunication system. The method for allocating a downlink radio resource in a base station includes retrieving a downlink radio resource allocated to a first mobile terminal if the first mobile terminal does not have a downlink packet, continuously checking whether or not there is a new downlink packet for the first mobile terminal, and retrieving a radio resource allocated to a second mobile terminal if there is a new downlink packet for the first mobile terminal and reallocating the retrieved radio resource to the first mobile terminal.