A neighbor cell list is formed, for use in a basestation of a cellular communications network. For each of a plurality of neighbor cells, a value of a first component is assigned, depending on whether or not the basestation can detect signals transmitted from said neighbor cell. A value of a second component is assigned, depending on a history of successful or unsuccessful handover attempts to said neighbor cell. The values of the first and second components are combined to form a weighting parameter, for use in determining a handover priority to be given to said neighbor cell in the neighbor cell list.