A method for reporting channel state information, CSI, from a mobile station to a base station of a mobile communication system in which a plurality of downlink component carriers and at least one uplink component carrier are configured for communication between the base station and the mobile station, the method comprising the following step performed by the mobile station: receiving from the base station a trigger message that triggers the reporting of CSI for at least one of the plurality of downlink component carriers, the trigger message being received in a subframe n Trigger; and transmitting to the base station, the triggered CSI for the at least one of the plurality of downlink component carriers based on reference signals present on the at least one of the plurality of downlink component carriers, in a subframe n Report later than n Trigger, wherein the reference signals, on the basis of which the CSI is to be reported, are present in a subframe n RS on the at least one of the plurality of downlink component carriers, where n RS is indicated by means of higher layer signaling, wherein the triggered CSI includes: a wideband channel quality indicator, CQI, value per codeword, which is calculated assuming use of a single precoding matrix in all sub-bands and downlink transmission on a set of sub-bands, S; and a selected single precoding matrix indicator, PMI, or a first and second PMI corresponding to the selected single PMI, wherein the single PMI is selected from a codebook subset assuming downlink transmission on the set of sub-bands, S, and wherein the reported PMI and the reported CQI values are calculated conditioned on a reported rank indicator, RI, or are calculated conditioned on RI = 1. receiving from the base station a trigger message that triggers the reporting of CSI for at least one of the plurality of downlink component carriers, the trigger message being received in a subframe n Trigger; and transmitting to the base station, the triggered CSI for the at least one of the plurality of downlink component carriers based on reference signals present on the at least one of the plurality of downlink component carriers, in a subframe n Report later than n Trigger, wherein the reference signals, on the basis of which the CSI is to be reported, are present in a subframe n RS on the at least one of the plurality of downlink component carriers, where n RS is indicated by means of higher layer signaling, wherein the triggered CSI includes: a wideband channel quality indicator, CQI, value per codeword, which is calculated assuming use of a single precoding matrix in all sub-bands and downlink transmission on a set of sub-bands, S; and a selected single precoding matrix indicator, PMI, or a first and second PMI corresponding to the selected single PMI, wherein the single PMI is selected from a codebook subset assuming downlink transmission on the set of sub-bands, S, and wherein the reported PMI and the reported CQI values are calculated conditioned on a reported rank indicator, RI, or are calculated conditioned on RI = 1. a wideband channel quality indicator, CQI, value per codeword, which is calculated assuming use of a single precoding matrix in all sub-bands and downlink transmission on a set of sub-bands, S; and a selected single precoding matrix indicator, PMI, or a first and second PMI corresponding to the selected single PMI, wherein the single PMI is selected from a codebook subset assuming downlink transmission on the set of sub-bands, S, and wherein the reported PMI and the reported CQI values are calculated conditioned on a reported rank indicator, RI, or are calculated conditioned on RI = 1.