Goal: The presentation assesses the relationship of the postsurgery cognitive changes to the side of surgery. Methods: In the sample of 41 adult patients (18 left-sided surgery, 23 right -sided), intelligence was evaluated by WAIS-R, memory by WMS-R (in a few patients by WMS). We used a comparison of average values of groups and three methods of reliable change indices (RCI) in individuals (Franzen, Iverson, 2000): standard deviation (±SD), and two methods of reliable difference scores by Chelune et al. (1993) and by Atkinson (1991). Results: There were no significant differences between groups in cognitive functions before surgery. On the average 19.7 months after surgery, patients with left-sided surgery have significantly lower general memory than patients with right-sided surgery (p=0.009). The average change betwe¬en pre- and postsurgical general memory is negative, e.i. worsening (-5.88) in left-sided surgery, and positive, e.i. improving (6.22) in right-sided surgery (p=0.001). In left-sided surgery, 17 patients were evaluated by memory test out of whom, after surgery, 3 patients' (17.6%) memory declined more than 1 SD. In the right-sided surgery, 23 patients were evaluated, out of whom, after surgery, 6 patients (26.1%) improved more than 1 SD, 1 patient (4.4%) declined more than 1 SD. Conclusion: Evaluation of neuropsychological changes relates to efforts to improve patients' quali-ty of life, dependent not only on epileptological efficiency of surgery, but also on changes in cognitive, especially memory functioning, which are possible after surgery.

        Key words: epilepsy, neurosurgery, cognitive changes-memory, neuropsychology, reliable change indices (RCI).