A method and apparatus for scheduling downlink packets in a mobile communication system are provided, in which a BS prioritizes MSs, while accounting for types of services provided to the MSs, generates one single-user candidate transmission format and M multi-user candidate transmission formats corresponding to a DRC value received from an MS with a highest priority level, estimates per-slot effective data rates for the single-user candidate transmission format and all of the multi-user candidate transmission formats, and transmits a downlink packet in a candidate transmission format having a maximum per-slot effective data rate.