Summary The proper function of the immune system is important for children with epilepsy, as any infection can cause or intensify the seizures, consequently aggravating the neurodevelopment condition of a young patient. The primary role in the correct functioning of the immunological system plays the specific immune response mechanisms with dominating role of the lymphocytes. In view of chronic, frequently many years’ administration of pharmacological agents, their possible effect on immunological indexes is very important. Aim The aim of this study was to evaluate the proportional participation and number of the lymphocytes and their subpopulation, as well as the NK cells in the peripheral vein blood of children treated because of epilepsy with valproic acid or carbamazepine Material and methods The research comprised 61 children aged 4 to 18, submitted to valproic acid or carbamazepine monotherapy for the period oscillating between 6 months and 5 years due to epilepsy. The patients were divided into 2 basic groups: I group – 29 children treated with valproic acid (VPA); I group – 32 children treated with carbamazepine (CBZ). The results were compared with the values obtained in the control group formed by 15 healthy children. The immune tests consisted in a single and synchronous evaluation of the lymphocytes in the peripheral vein blood of the flow cytometry. Results 1. No significant quantitative differences have been observed within the lymphocytes B, T and their subpopulation or NK cells in the children treated for epilepsy with valproic acid or carbamazepine. 2. In the children treated with carbamazepine, a significant relation between the treatment duration and the reduction of the CD8+(Ts) lymphocyte number as the treatment proceeded. Conclusions On the ground of the tests carried out no negative impact of the chronic valproic acid or carbamazepine treatment on the immune and hematopoietic system functions has been observed.