Competing visual stimuli lead to slower responses to targets. This response competition must be resolved before correct responses are executed. Neuroimaging suggests that response competition monitoring may be subserved by an integrated neural network including the anterior cingulate cortex (ACC). In this study, 1 patient with a parietal lesion (Patient J.S.) and 1 with an ACC lesion (Patient G.M.) were presented with 2 ranker tasks; 1 required verbal identification of color targets, and the other required an opposite response to targets (e.g., see red and say 'green'); a control group was also tested. For controls, perceptually incongruent rankers interfered with the ability to inhibit prepotent responses to targets. Patient J.S. performed in a similar manner, even when rankers appeared in the neglected field. Patient G.M. demonstrated reduced interference effects for contralesional rankers. Results are discussed in terms of goal-directed selective attention and response competition monitoring.