Bipolar major depression differs considerably from unipolar major depression with regard to the efficacy of treatment with antidepressants. In bipolar depression, response to treatment with antidepressants is disappointing. Whether response to electroconvulsive therapy (ECT) differs between bipolar and unipolar depression remains unclear. Therefore, this systematic review investigates the relative efficacy of ECT in both forms of depression. Relevant cohort studies were identified from a systematic search of the PubMed electronic database. Six studies were included in this meta-analysis. In this meta-analysis, the overall remission rate was 50.9% (n = 402/790) for patients with unipolar depression and 53.2% (n = 168/316) for patients with bipolar major depression. A pooled odds ratio (OR) and confidence interval (CI) were calculated using random-effects meta-analysis with the Mantel-Haenzel method. This analysis shows similar efficacy of ECT in patients with unipolar and bipolar depression (OR = 1.08, 95% CI: 0.75-1.57). ECT appears to be equally effective for both bipolar and unipolar depression and the remission rates are encouraging, especially for bipolar depression. © 2012 John Wiley and Sons A/S.