The invention describes a flow control method to control HS-DSCH data streams over UTRAN Iub and Iur interfaces. Two credit assignment schemes are also described. A radio network node at which the flow control method executes is proposed. Finally a computer program product for execution of the flow control method and the credit assignment schemes is described. The control of separate user data flows is coordinated by Node-B and data transport over the Iub and Iur interfaces is adapted to data transfer over the Uu interface. The main advantage is that buffering can be primarily maintained in SRNC. It is shown that the proposed flow control method can significantly reduce Node-B's buffer level when compared to a scheme where the control of individual data flows is performed independently of each other. It is also shown that the negative impact on the quantity of flowing data is generally minor.