The anterior cingulate cortex (ACC) has been proposed as part of the brain's attentional control network, but the exact nature of its involvement in cognitive and motor operations is under debate. Assessing effects of human ACC damage directly addresses the problem of ACC function. We report that executive control processes of a patient with a focal right hemisphere anterior cingulate lesion were not compromised. However, her performance level depended on the response modality used. Under the same task requirements, she was impaired when giving manual responses, but not vocal responses. Thus, we provide neuropsychological evidence for functional specialization within the human ACC.