According to one aspect of the teachings herein, a wireless device operating in a wireless communication network determines the difference in signal arrival times with respect to first and second cells, and the device and/or the involved wireless communication network uses the difference to control one or more aspects of Carrier Aggregation, CA, operation for the wireless device. For example, there may be a maximum timing difference defined for the wireless device, e.g., as a function of its inherent capabilities, and the wireless device may evaluate the timing difference of a second cell that is a candidate of aggregation into its CA configuration, or that may be a candidate for activation as a serving cell within a CA configuration, with respect to a first cell that is already in use as a serving cell for the wireless device.