The invention relates to a radio base station (102) and method in a radio base station of a cellular communications system (100) for controlling self-interference. The radio base station (102) supports communication with a user equipment (101) using multiple uplink and multiple downlink carriers (104a, 104b, 105a, 105b). The method comprises detecting a degraded downlink performance on a downlink carrier (105a) due to self-interference by determining that a set of predefined conditions applies. The method further comprises executing, in response to detection of the degraded downlink performance, an action to reduce self-interference between the uplink and downlink carriers (104a, 104b, 105a, 105b). The action is one of: uplink scheduling to reduce self-interference, deactivation of a secondary uplink carrier (14a, 104b), deactivation of a secondary downlink carrier (105a, 105b), and initiation of carrier reconfiguration to reduce self-interference. Accordingly, benefits of using multi-carrier operation may be balanced against a possible associated drawback of degraded downlink performance due to self-interference.