QT dispersion (QTd) is a measure of interlead variations of the surface 12-lead electrocardiogram (ECG). Increased QTd, found in various cardiac diseases, reflects cardiac instability and is associated with increased risk for cardiac death. Research suggests a link between antipsychotics, ECG abnormalities (QT prolongation) and increased sudden cardiac mortality rates. However, QTd analysis has been scarcely investigated in schizophrenia patients. We calculated QTd in 20 medicated psychotic inpatients with schizophrenia, before and 3 days after electroconvulsive therapy (ECT), concomitantly with Brief Psychiatric Rating Scale (BPRS) assessment. QT interval and the rate-corrected QT (QTc) were abnormally prolonged before ECT. However, although QT was significantly shortened, QTc showed only a marginal decrease after ECT. QTd, the rate-corrected QTd, as well as BPRS, showed a significant decrease after ECT. Further large-scale studies are warranted to determine if QTd can serve as a marker for response to ECT, and if it is a risk factor for sudden cardiac death in schizophrenia patients.