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 t