Topiramate is the new antiepileptic drug, which is related with high efficiency in the reduction seazures, and also whit high prevalention of cognitive adverse events. Purpose of study is to define the relationship between efficiency topiramate in control of epileptic seizure and the apperance of cognitive adverse events. In the prospective stady we followed 40 adult patients with refractory epilepsy, which treatment took place on the Institute of neurology Clinical center of Serbia. The efficacy of treatment was estimated as the ratio of the total number of seizures during the last two months before the introduction of topiramate (on basic antiepileptic therapy) and during the last two months on stable (200mg/day) dose of topiramate.All patients are neuropsychological tested twice. First time before the start of therapy with topiramate, and next time two months after the achieving of stable dose. We used neuropsychological tests for evaluation attention, concentration, visual and verbal memory, speech, executive functions, divergent opinion and visual construction abilities. Patients with good success of topiramate in control of the seizures had worse scores on cognitive measurements than patients in whom topiramate was not demonstrated efficacy in treating epileptic seizures. Our findings indicate that the appearance of cognitive adverse events of topiramate possible in patients with reduction of seizure after the introduction of drug. This suggests that the same mechanism topiramat achieve a positive therapeutic effect and adverse effect on cognition in people with epilepsy.