The invention concerns a method and an apparatus implementing the method. In the method is received a neighbor cell relation list and a request to report new cells not included in the neighbor cell relation list to the mobile node to a mobile node. The mobile node detects at least one new cell not included in the neighbor cell relation list and stores information regarding the at least one new cell not included in the neighbor cell relation list in a memory. The mobile node determines whether a threshold number of new cells not included in the neighbor cell relation list have been stored in the memory of the mobile node. In response to reaching the threshold number, the mobile node preparing for transmitting the information regarding the at least one new cell not included in the neighbor cell relation list to a radio network node.