1. A method for collecting user activity information in a telecommunications system comprising a first telecommunications node handling signaling messages of the terminal of a user and a second telecommunications node handling registration information of said user, comprising the steps of: a) sending from the first node to the second node a message notifying a registration event of the user, and b) updating by the second node registration information of said user according to the content of said message; wherein step a) further comprises: a1) sending in said message an information element indicating whether said user has been involved in a service provided during a registration period comprised between a previous registration event of said user and the registration event notified in the step “a”, and step b) further comprises the step of: b1) updating by the second node activity information of said user according to said information element.