A method in a radio network node for ranking cells within a group of cells in a cellular network is provided. The radio network node is serving a first cell, in the group of cells. The radio network node receives (201) power level measurements from one or more user equipments. The power level measurements respectively indicate a power level in at least one cell of the group of cells where the respective one or more user equipments is active. The radio network node then ranks (202) importance of the cells in the group of cells, both based on the power level measurements, and on the number, for each cell out of the group of cells, of user equipments whose power level measurements indicate that the respective cell has the highest power level.