A user equipment, UE, comprising: an information size determination section configured to determine a basic information size of control information; and a receiver configured to monitor the control information based on the determined basic information size, wherein: the information size determination section determines the basic information size of the control information mapped on a UE specific search space in a downlink component carrier, to which only downlink assignment information is assigned, based on an information size determined from a bandwidth of the downlink component carrier; the information size determination section determines the basic information size of control information mapped on a common search space in the downlink component carrier based on the larger one of the information size determined from the bandwidth of the downlink component carrier and an information size determined from a bandwidth of an uplink component carrier; and the information size determination section determines the basic information size of the control information mapped on a search space in another downlink component carrier, to which the uplink assignment information is assigned, based on the larger one of an information size determined from a bandwidth of the other downlink component carrier and an information size determined from the bandwidth of the uplink component carrier. an information size determination section configured to determine a basic information size of control information; and a receiver configured to monitor the control information based on the determined basic information size, wherein: the information size determination section determines the basic information size of the control information mapped on a UE specific search space in a downlink component carrier, to which only downlink assignment information is assigned, based on an information size determined from a bandwidth of the downlink component carrier; the information size determination section determines the basic information size of control information mapped on a common search space in the downlink component carrier based on the larger one of the information size determined from the bandwidth of the downlink component carrier and an information size determined from a bandwidth of an uplink component carrier; and the information size determination section determines the basic information size of the control information mapped on a search space in another downlink component carrier, to which the uplink assignment information is assigned, based on the larger one of an information size determined from a bandwidth of the other downlink component carrier and an information size determined from the bandwidth of the uplink component carrier. the information size determination section determines the basic information size of the control information mapped on a UE specific search space in a downlink component carrier, to which only downlink assignment information is assigned, based on an information size determined from a bandwidth of the downlink component carrier; the information size determination section determines the basic information size of control information mapped on a common search space in the downlink component carrier based on the larger one of the information size determined from the bandwidth of the downlink component carrier and an information size determined from a bandwidth of an uplink component carrier; and the information size determination section determines the basic information size of the control information mapped on a search space in another downlink component carrier, to which the uplink assignment information is assigned, based on the larger one of an information size determined from a bandwidth of the other downlink component carrier and an information size determined from the bandwidth of the uplink component carrier.