Registering a user in a communication network

The present invention describes a registration method wherein a user is registered in a communication network. According to a first aspect, a registration message is used, which comprises a header field for defining at least one other identity of the subscriber. According to a second aspect, a registration message is used, which comprises an identity information in its payload portion, said identity information defining at least one other identity of the subscriber. According to a third aspect, a one-by-one registration is performed based on an identity information stored at the terminal device, said identity information defining at least one other identity of the subscriber. Thus, the user or subscriber can register some or all of his public identities at once with one registration procedure. Furthermore, the subscriber can utilize his identities smoothly and easily, and at the same time prevent unwanted incoming calls. Additionally, the subscriber can utilize his public identities smoothly and easily by grouping the public identities under user profiles or under private identities.