Abstract: A method and apparatus for transmitting/receiving control information to support High Speed Downlink Packet Access (HSDPA) in a WCDMA communication system are provided. When transmitting new packet data, a Node B sets a New data Indicator (NI) to a specific bit value indicating an initial transmission for the packet data. Upon receipt of a retransmission request for the packet data, the Node B sets the NI as the inverse of a previous NI. If an redundancy version (RV) representing a constellation and a data type for packet data, is set to a specific value indicating an initial transmission, the Node B set the NI to the inverse of the specific bit value regardless of the previous NI. A User Equipment (UE) receives control information including the NI and the redundancy version (RV) and determines that the packet data is initial transmission data or retransmission data, according to the NI and the RV.