A method and an arrangement in a radio network node for reconfiguring mappings from Carrier Indicator Field-values to component carriers are provided. Each CIF-value is mapped to a respective component carrier comprising a respective shared data channel. Each respective shared data channel corresponds to at least one downlink control channel carrying said each CIF-value. The radio network node reconfigures mappings from CIF-values to component carriers, while at least one mapping of CIF-value to component carrier is maintained. The component carrier of said at least one mapping from CIF-value to component carrier comprises said at least one downlink control channel and a shared data channel corresponding to said at least one downlink control channel. The radio network node sends at least one of the reconfigured mappings from CIF-values to component carriers to the user equipment.