Electroconvulsive therapy (ECT) is a highly effective treatment for severe depressive disorder. Efficacy and cognitive outcomes have been shown to depend on variations in treatment technique. A high resolution finite element model of a human head was generated from MRI scans and implemented with tissue heterogeneity and an excitable ionic neural model incorporated in the brain. The model was used to compare the effects of three common ECT electrode configurations, including the spatial profiles of electric field and excitation in the brain. The results showed that electrode placement has a significant effect in determining the spatial extent of activation in different brain regions, which would account for differences seen in clinical outcomes.