A signaling method for transmitting packet data including information indicating an MN ID of one target access terminal (AT) among a plurality of ATs from a packet data service node (PSDN) to the target AT in a mobile communication system including a service system connected to the PDSN and a data location register (DLR), a plurality of access systems each having an access network controller (ANC) connected to the service system, and a plurality of access terminals (ATs) for communicating by radio with the access systems. In the signaling method, upon receipt of a message informing the access system of arrival of the packet data, the access system transmits a Paging Request message to the DLR. Upon receipt of the Paging Request message, the DLR storing location information of the plurality of ATs within areas of the plurality of access systems searches a location of the target AT. The DLR transmits a Paging Response message including a return of the Paging Request message through the service system to a, target access system where the target AT is located among the plurality of access systems, and transmits a Paging Command message to the target AT. Upon receipt of a Connection Request message for the packet data from the target AT, the service system transmits the packet data to the target AT through the target access system.