Only the organic and cryptogenic forms of frontal lobe epilepsy have been admitted by the ILAE, but according to several reports in the literature, it probably exists also an idiopathic form, at present not well recognized.To study the differences between the organic and the cryptogenic forms of frontal epilepsy in our patients, that might indicate the presence of idiopathic cases within the presumed cryptogenic group.All patients diagnosed of frontal lobe epilepsy, EEG registered, at the neuropediatric clinic of our hospital during 1993-1996, were selected: 30 patients under 14 years of age that were classified as organic (10 cases) or cryptogenic (20 cases) according to CT or MRI findings. The Mann-Whitney test and the Fisher exact test were performed for statistical analysis. Five patients with peculiar neurocognitive symptoms, epilepsy-related, are described in detail.Significative differences between the organic and cryptogenic forms of frontal lobe epilepsy were not found except for the tendency of cryptogenic EEG foci to spread beyond the frontal lobe, to generalize and to be associated with foci of other localizations. Epileptic status, either convulsive or not convulsive, were a frequent complication in both groups.The identification of an idiopathic form of frontal lobe epilepsy is difficult by its low prevalence as compared to the cryptogenic and organic forms, by the tendency of frontal seizures to become epileptic status, which predicts an intractable epilepsy, and by the clinical characteristics essential to frontal discharges: heterogeneity, frequent impairment of consciousness and specially the neurocognitive semiology, including dementia, that occurs as a critic or paracritic phenomenon, and that sometimes may develop or be accentuated by antiepileptic medication.