Methods and systems for tracking mobile communication terminals based on their identifiers. The disclosed techniques identify cellular terminals and Wireless Local Area Network (WLAN) terminals that are likely to be carried by the same individual, or cellular and WLAN identifiers that belong to the same multi-mode terminal. A correlation system is connected to a cellular network and to a WLAN. The system receives location coordinates of cellular identifiers used by mobile terminals in the cellular network, and location coordinates of WLAN identifiers used by mobile terminals in the WLAN. Based on the location coordinates, the system is able to construct routes that are traversed by the terminals having the various cellular and WLAN identifiers. The system attempts to find correlations in time and space between the routes.