The invention relates to a method for accessing an Internet protocol Multimedia Subsystem type subsystem, said subsystem. According to the invention, a device is firstly connected to a mobile communication network, as a visited network, said first network. The method comprises the following steps. The first network sends to the device a first message comprising current location data relating to a location where the device is currently present. The device analyzes whether at least one roaming rule associated with the current location data is or is not stored within the device. The at least one roaming rule includes, each, at least one parameter for accessing the subsystem. And if the device does store the at least one roaming rule associated with the current location data, then the device sends to the subsystem a second message including a request for connecting to the subsystem. The invention also pertains to a corresponding device.