We studied the association between RGS4 (rs951436) polymorphism and treatment response in electroconvulsive therapy (ECT) as well as risk of treatment-resistant depression. The study sample consisted of 119 patients with major depressive disorder (MDD) and 384 healthy control subjects. RGS4 polymorphism was not associated with treatment response in ECT or risk of MDD. According to the present data, the impact of RGS4 genotype is not decisive in major depressive disorder. The results provide preliminary data on the impact of RGS4 polymorphism in treatment response in ECT.