Problems related to the study of the coagulation status of patients during the neonatal period are well known to neonatologists. Hemorrhagic disorders in the period of the newborn can be caused by deficiency of vitamin K-dependent factors, intrauterine infection, hereditary coagulopathy, primary and secondary disorders of platelet hemostasis and a number of other reasons. Clinical manifestations of hemorrhagic syndrome in a newborn child are non-specific, allowing to suspect the type of blood flow, however, conducting selective hemostatic therapy is possible only after laboratory identification of the disease. Among congenital coagulopathies, hemophilia A is the most frequently encountered, while clinical manifestations of the disease occur during the neonatal period only in the case of the presence of a severe form of the disease. Meanwhile, in the practice of pediatricians and neonatologists, vascular tumors are encountered quite rarely, including Kazabach-Merritt syndrome – a potentially life-threatening condition in which hemangioendotheliomas grow rapidly and reach gigantic sizes, combined with severe thrombocytopenia and coagulopathy. In this article, two clinical cases of severe hemophilia A in newborn boys with basic factor VIII activity of less than 1% are presented, as well as a case of infantile hemangioendothelioma of the liver in a newborn baby. In the article, the directions of the laboratory search for disorders of primary and secondary hemostasis were analyzed, which allowed the diagnosis to be clarified and the appropriate hemostatic therapy to be selected.