Disclosed is a method for resuming header decompression by receiving multimedia broadcast/multicast service (MBMS) packet data having compressed headers in a mobile communication system providing the MBMS. The method includes the steps of detecting a moving of user equipment (UE) receiving the MBMS into a new cell from an old cell, copying and storing old header decompression context information used in the old cell, initializing a dynamic part to decompress headers of packet data for the MBMS and waiting for an IR-DYN packet until the IR-DYN packet has been received in the UE, in order to update the old header decompression information, creating a new header decompression context through updating the old header decompression information by using the IR-DYN packet when the IR-DYN packet has been received in the UE, and decompressing the headers of the packet data for the MBMS transmitted from the new cell by using the new header decompression context.