A method is provided for transmitting a power headroom report at a user equipment (UE) in a wireless communication system. The UE configures a first cell group having a primary cell (PCell) and a second cell group having one or more secondary cells (SCells). The UE transmits the power headroom report. If the first cell group and the second cell group are managed by a same base station, the power headroom report indicates power headroom information regarding the first and second cell groups. If the first cell group and the second cell group are managed by different base stations, the power headroom report indicates power headroom information regarding only one of the first cell group and the second cell group.