In the presurgical evaluation of children and juvenile patients with refractory focal epilepsy, the main challenge is to localize the point of seizure onset as precisely as possible. We compared results of the conventional electroencephalography-functional magnetic resonance imaging (EEG-fMRI) analysis with those obtained with a newly developed method using voltage maps of average interictal epileptiform discharges (IEDs) recorded during clinical long-term monitoring and with the results of the electric source imaging (ESI).