Objective of the research: to determine the prevalence of various nosological forms of rare (orphan) diseases in pediatric population of the Russian Federation (RF) to expand and improve diagnostic resources. Materials and methods: the prevalence of individual nosological forms of life-threatening and chronic progressive rare diseases in pediatric populationwas calculated according to the regional segments of the Federal Register. The results of fetus ultrasound screening, samples for biochemical screening and coverage of children with neonatal screening in the Russian Federation are evaluated. Results: the study revealed an increase in the prevalence of rare diseases due to the majority of nosological forms without changing their structure. For many nosological forms, an increase in their prevalence was accompanied by a decrease in the proportion of children among all patients. A high coverage of pregnant women with ultrasound screening was revealed. The number of fetuses with identified congenital malformations did not exceed 2%. Disorders during biochemical screening tests were recorded in 3-5% of cases. Neonatal screening coverage was not more than 95%. In 2013-2018, 49, 9 million screening tests were performed and 7, 7 thousand newborns with congenital and hereditary diseases were identified. The necessity of including in the neonatal screening of orphan diseases in which the use of pathogenetic therapy is possible is substantiated. Conclusion: determining the prevalence of various nosological forms of orphan diseases is extremely important and necessary to expand and improve their diagnosis, which will increase the detection of this pathology. © 2020, Pediatria Ltd.. All rights reserved.