A method for Mobility Management MM in a system architecture supporting mobility between different access systems having separate Core Network CN-level MM entities while using common MM Area is provided. When a User Equipment UE leaves the coverage of a first access system where it is in a Non Radio Connected state as seen from Radio Access Network RAN, but seen in Connected State from CN-level MM entity, for the coverage of a second access system where it is in Idle state as seen from CN-level MM entity, the UE is put into Idle state as seen from CN-level MM entity of said first access system.