Electroconvulsive therapy (ECT) administration rises in frequency with age, with older depressed adults often showing clinical features predictive of good response. Recent reviews suggest that older people experience few if any long-term cognitive adverse effects after contemporary ECT, despite their increased vulnerability to these. However, the broader clinical validity of research findings is not assured as most studies of ECT-related cognitive effects do not discuss cognitive test nonparticipants. This study examines whether cognitive test participants and nonparticipants are comparable.