Objective The authors examined the relationship between hippocampal volume and acute electroconvulsive therapy (ECT) outcomes. Methods Depression was measured by Montgomery-Asberg Depression Rating Scale (MADRS) scores, and hippocampal volume was assessed by magnetic resonance imaging. Results After controlling for baseline MADRS score, larger right-hippocampal volume was associated with higher MADRS scores after an index course of ECT. Conclusion These results are the converse of those obtained in a study assessing the relationship between hippocampal volume and pharmacotherapy. The findings suggest a need for further study in this area.