The invention relates to a method of and a system for transferring a communication session from one service area (101) to another (102), where each service area is associated with a transcoding proxy (111, 112) for transcoding communication sessions established in said service area to and from a format suitable for a mobile device (104). A gateway server (103) relays the communication session from a content server (105, 106, 107) via the appropriate transcoding proxy to the mobile device (104). When the mobile device (104) moves to the second service area (102), the second transcoding proxy (112) is contacted and session handling is transferred thereto. The transfer operation is transparent to the content server, so the session between mobile device (104) and content server (105, 106, 107) stays intact. The invention also relates to a mobile assistant server, a transcoding proxy and a mobile device for use in said system.