A method and apparatus for controlling an active time period during a Discontinuous Reception (DRX) operation in a User Equipment (UE) in a mobile communication system. The method includes starting, in the UE, a first timer to monitor control data via a shared control channel, the control data being associated with user data to be transmitted; and starting, in the UE, a second timer, when the control data indicating a new transmission of associated user data is received via the shared control channel while the first timer is running, or restarting, in the UE, the second timer, when the control data indicating a new transmission of associated user data is received via the shared control channel while the second timer is running.