A method and apparatus for power control for wireless transmissions on multiple component carriers corresponding to multiple serving cells associated with multiple timing advances are disclosed. A wireless transmit/receive unit (WTRU) may determine transmit powers for a first physical channel for a first serving cell in a first timing advanced group (TAG) and a second physical channel for a second serving cell in a second TAG. The first TAG may less timing advanced than the second TAG. The WTRU may determine a WTRU configured maximum output power (PCMAX) for an overlapping portion, which may be a portion of a transmission of the first channel in a first subframe that overlaps in time with a portion of a transmission of the second channel in a next subframe. The WTRU may adjust the channels such that a sum of their transmit powers in the overlapping portion does not exceed the determined PCMAX.