Anterior cingulate integrity may be required for antidepressant response. To assess anterior cingulate processes related to treatment response, we studied error-related negativity and error positivity produced during an emotional go/no-go challenge, a task activating the rostral anterior cingulate. Twelve elderly patients with major depression, treated with escitalopram 10 mg daily, were studied. Patients who remained symptomatic after 8 weeks of treatment had larger error-related negativity and smaller error positivity amplitude compared with patients who achieved remission. The error-related negativity is elicited during conflict detection and the error positivity reflects the emotional reaction to error. Thus, these findings suggest that two distinct conflict-processing functions of the anterior cingulate are important for antidepressant response of geriatric depression.