Objective. Difficulties in the area of executive functions, social adjustment and behavior are observed in patients with JME and stressed to frontal lobe involvement in this electro-clinical syndrome. The contribution of extra-frontal structures to cognition in JME is also challenged. Methods. We prospectively analyzed clinical and diagnostic data and prognosis of 83 JME patients (36 male, 47 female) aged 16 to 31.5 years (mean 21.4), with mean seizure onset of 13.3 years (range 8.5–18.7). Cognitive functions are assessed by the Halstead–Reitan Neuropsychological Test Battery for adolescents and younger adults. Retest was done for mean 5 years after the initial test. Patients with JME were compared with 35 healthy controls, sex-, ageand education-matched, and comparable subjects. Results. Complete seizure control was achieved in 63 (75.9%) patients mainly with valproate (54 patients). Pseudo-resistant seizures occurred in 89.6%, while JME was refractory in14.5% patients. Seizure and drug freedom was noted in 12% patients. No cognitive dysfunctions were disclosed in 31 (37.3%) patients. No clear and significant association between test-results and epilepsy-related parameters, including type of antiepileptic drug, level of seizure control and JME duration. Patients diagnosed with JME scored significantly below controls on frontal tasks (Wisconsin test-perseverations, TMT-B, Stroop test, verbal categorical and phonemic fluency tests). No intellectual decline was stated over clinical follow-up. Poor performance was found not only on tests measuring frontal functions (attention, executive functions, working memory, mental flexibility, concept formation and planning) but also on tasks assessing delayed verbal and visual learning and naming. Psychiatric disorders were noted in 38 (45.8%) patients. High rates of anxiety, phobias and somatization disorders (25.3%) and mood disorders (18.1%) were seen in patients with JME. Depression associated with personality disorder prevailed. Only 22.9% patients are employed. Conclusions. Juvenile myoclonic epilepsy may be a non-uniform condition. Different still elusive mechanisms could underlie the clinically observed differences in prognosis, cognitive and psychological functioning.