Electroconvulsive therapy (ECT) is a rapidly acting and highly effective treatment for severe and life threatening conditions seen in affective and schizophrenic diseases. Notwithstanding its therapeutic benefits, ECT remains controversial because of seizure induction, cognitive side effects, memory dysfunction and effects on cerebral physiology. These factors have raised the concern that ECT produces structural and functional brain damages. This issue continues to have a major impact on the acceptance of ECT as a therapeutic modality, both within the medical community and in public opinion. A close look at incidence, type, severity, neurofunctional and -anatomical correlates, aetiology and therapeutic approaches of the adverse cognitive effects attributed to ECT may contribute to rational and objective handling of this topic. The final chapter deals with the issue of whether ECT causes brain damage.