Electroencephalographic (EEG) monitoring during electroconvulsive therapy (ECT) sessions is essential for two reasons. First, the EEG monitoring during ECT sessions is the most effective method to detect a prolonged seizure. Avoid prolonged crisis allows to minimize the brain side effects of ECT. Indeed, prolonged seizures, in the short-term, increase the risk of post-ECT status epilepticus, rare but serious complication of ECT, and, in the medium-term, increase the risk of poor cognitive tolerance without increasing clinical efficacy. Second, EEG monitoring of ECT sessions, additional to clinical monitoring, helps to confirm the presence of an adequate or optimal seizures and allows to adjust the electrical stimulation parameters in order to maximize the efficacy of ECT treatment. This paper proposes a help to read the EEG during ECT sessions and a decision tree based on the EEG reading. The aim was not to summarize the whole conduct of ECT treatment in psychiatry, but to emphasize the centrality of clinical neurophysiology in some psychiatric therapeutic strategies.