Abstract : Electroconvulsive therapy (ECT) is one of the oldest and most effective methods to treat many psychiatric disorders. Succinylcholine is a short-acting depolarizing skeletal muscle relaxant used to relax muscles and facilitate patient control during intubation, mechanical ventilation, and surgical procedures. The aim of this study was to compare the probable complications and hemodynamic changes created as a result of applying 0.3 and 0.6 doses of Succinylcholine in candidates of ECT. In this clinical trial at Isfahan university hospital, 40 ECT candidate patients were randomly divided into two groups of 20 patients receiving 0.3 and 0.6 Milligrams per Kilogram dose of Succinylcholine. The age, sex, height, weight, and body mass index (BMI) of patients were recorded. Before induction of anesthesia (baseline) and 1, 5, 10, and 20 minutes later, symptoms like systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and oxygen saturation (SPO2) measured and compared between two groups. There were no significant differences between the two groups regarding primary data and symptom values (P> 0.05). In patients that received 0.6 mg/kg of Succinylcholine, the prevalence of hypoxia and duration of apnea were significantly higher and the seizure duration was considerably shorter. Administration of Succinylcholine with 0.3 mg/kg lead to fewer complications including frequency and duration of apnea.