A method for power headroom reporting in a radio communication system for a component carrier on which a user equipment transmits uplink control information on a Physical Uplink Control Channel comprising: calculating, by said user equipment, a power headroom for said component carrier, when said user equipment has no current transmission on the Physical Uplink Control Channel, using at least one known value for at least one parameter associated with said Physical Uplink Control Channel to calculate said power headroom since a value cannot be obtained for said at least one parameter; wherein said at least one known value is a value known by both said user equipment and an eNodeB to which said user equipment is connected, wherein said at least one parameter includes at least one of: (a) h c (n CQI, n HARQ), which represents an amount by which power is adapted to the number of control information bits that are transmitted on said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel, (b) Δ F_PUCCHc, which represents a relative performance difference between Physical Uplink Control Channel format la and said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel, and (c) δ PUCCHc (i-k m), which represents a transmit power control command associated with said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel; and transmitting, by said user equipment, a power headroom report based on said calculated power headroom. calculating, by said user equipment, a power headroom for said component carrier, when said user equipment has no current transmission on the Physical Uplink Control Channel, using at least one known value for at least one parameter associated with said Physical Uplink Control Channel to calculate said power headroom since a value cannot be obtained for said at least one parameter; wherein said at least one known value is a value known by both said user equipment and an eNodeB to which said user equipment is connected, wherein said at least one parameter includes at least one of: (a) h c (n CQI, n HARQ), which represents an amount by which power is adapted to the number of control information bits that are transmitted on said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel, (b) Δ F_PUCCHc, which represents a relative performance difference between Physical Uplink Control Channel format la and said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel, and (c) δ PUCCHc (i-k m), which represents a transmit power control command associated with said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel; and (a) h c (n CQI, n HARQ), which represents an amount by which power is adapted to the number of control information bits that are transmitted on said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel, (b) Δ F_PUCCHc, which represents a relative performance difference between Physical Uplink Control Channel format la and said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel, and (c) δ PUCCHc (i-k m), which represents a transmit power control command associated with said Physical Uplink Control Channel on said component carrier when the user equipment has a transmission on the Physical Uplink Control Channel; and transmitting, by said user equipment, a power headroom report based on said calculated power headroom.