Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare disease. Few states in developing countries have an adequate management of HAE, but none of them belongs to the former USSR area. This study analyses data from C1-INH-HAE patients from Belarus. Data about clinical characteristics, genetics, access to diagnosis and treatment were collected from 2010 by the Belarusian Research Center for Pediatric Oncology, Hematology and Immunology in Minsk. A questionnaire about attacks, prophylactic (LTP) and on-demand therapy (ODT) was administered to patients. We identified 64 C1-INH-HAE patients belonging to 26 families, 27 (42.2%) of which were diagnosed in the last 3 years. The estimated minimal prevalence was 1:148000. Median age at diagnosis was 29 years, with diagnostic delay of 19 years. Thirty-eight patients answered a questionnaire about therapy. Twenty-seven patients underwent ODT: 9 (33.3%) with appropriate treatments, and 18 (66.7%) with inappropriate treatments. Nine patients used LTP with attenuated androgens and eleven recovered spontaneously. Thirty-two patients answered a questionnaire about attacks and triggers: 368 angioedema attacks were reported, with an average of 10 attacks per year. We found 24 different SERPING1 variants: 9 missenses, 6 in splice sites, 6 small deletions, 2 nonsense, 1 large deletion; 7 have not been previously described. De novo variants were found in 11 patients. C1-INH-HAE diagnosis and management in Belarus is improved as seen from the high number of new diagnosis in the last 3 years. Next steps will be to reduce the diagnostic delay and to promote the LTP and OTD.