Purpose: to study the role of cellular immunity in the development of retinopathy of prematurity (ROP).Material and methods. 87 children were tested, including 60 with III — V stage ROP and posterior aggressive retinopathy that had gestational age from 25 to 32 weeks at birth, aged 1 month to 1 year (study group) and 27 healthy children of the same age (control group).Results. No statistically significant differences of immunological parameters were revealed within the groups of children aged 1 to 3 months, 3.5 to 6 months, and 6.5 to 12 months. The gestational age at birth had no effect on the parameters studied. With increasing severity of ROP amid reduced indicators of T-regulatory cells, the number of B-cells (CD19 +) grew, T-natural killer cells (CD3 -/CD16 +CD56 +) reduced significantly (p < 0.05), and the number of CD4+ T-cells reduced showing the significance of (p < 0.01–0.05).Conclusion. The obtained data testify to the emergence of autoimmune reactions and a decrease in the level of regulatory T-cells in a premature child, more pronounced in severe stages of ROP.