Modern electroconvulsive therapy (ECT) is a non-pharmacological and biological treatment that is clinically effective and safe. ECT is used in the treatment of many psychiatric disorders, some neurological diseases, and psychiatric emergencies requiring a rapid and life-saving clinical re-sponse. Generalized seizures of the central nervous system induced by the electrical stimulation of ECT are an essential component of the therapeutic effects, which are attributed to the various neuronal responses of the brain. Modern ECT is conducted under general anesthesia, given to the extent of loss of consciousness, followed by administration of a muscle relaxant, and ECT with minimally appropriate electrical stimulation. ECT optimization has the main objective of en-suring maximum clinical efficacy and safety with minimal adverse events through adequate gen-eralized seizures. Since its first introduction in clinical practice in 1938, many studies have been carried out and advances made to enhance the therapeutic effects of ECT and address the ad-verse events associated with it. As a result, there have been developments such as the use of a square wave instead of a sine wave, various electrode placements, dose titration methods, sei-zure thresholds, general anesthesia with muscle relaxation, session scheduling, monitoring of electroencephalograms (EEG) and electromyograms, etc. and these have been applied to actual clinical practice. Research on the clinical characteristics and the optimal ECT parameters to in-crease the efficacy of seizures is still ongoing. In this review, various factors associated with ECT such as EEG monitoring, motor seizures, electrode placements, stimulation dose and titration, seizure evaluation and adequacy, and the ECT algorithms are discussed to improve the efficacy of modern ECT as a useful treatment for psychiatric disorders.