A method and apparatus for controlling header compression and decompression for a link of a packet data network, wherein a predetermined header extension size for the link is initially set, and wherein a packet which will not be used as reference for subsequent decompression is transmitted from the compressor to the decompressor, if an extension header list of a size larger than the predetermined header extension size has been received. At the decompressing side, the transmission of an acknowledgement is suppressed, if an extension header list of the size larger than a predetermined header extension size configured at the decompressor has been received. Thereby, inconsistency of compression context between compressor and decompressor is prevented and a higher compression efficiency is achieved since there is no need to repair the context and correctly decompressed packets can be delivered to upper network layers without discarding any packets.