A method of providing access to an IP multimedia subsystem (IMS) for a subscriber (UE) comprises the steps of providing an home interface entity (HGGSN) with access network data (MCC′,MNC′) identifying the access communication network (AN), sending a message comprising the access network data (MCC′,MNC′) from an home interface entity (HGGSN) to serving means (HSS), comparing the home network data (MCC,MNC) and the access network data (MCC′,MNC′), checking if the subscriber (UE) is allowed to roam based on a set of predefined criteria when the result of the comparing step is false, and sending a message comprising the access network data (MCC′,MNC′) to at least one of call state control functionality means (CSCF) when the result of the checking step is true.