It has been observed that immunological reactivity of neonatal leukocytes is diminished. It seems to result from lymphocytes immaturity. In the present study we have evaluated the phenotype of cord blood lymphocytes with the use of flow cytometry. In neonates we have observed the increase in the absolute number of CD1a and CD7 positive lymphocytes as well as CD2, CD3, CD4, CD8, CD16, CD19 and CD20 positive, while number of CD57 positive cells was significantly decreased. The ratios of CD4/CD8 and T/B lymphocytes were similar to the corresponding ratios observed in adults. Our results have shown the presence of immature lymphocyte population as well quantitative depletion of subpopulation of CD57 cells, what may pose an increased risk of infection in neonates. Nevertheless, increased number of T and B lymphocytes with mature phenotype along with normal ratio of lymphocyte subpopulations and increased number of CD16 positive cells (NK cells), may explain phenomenon of good health among majority of newborns.