Background. The RAG1 and RAG2 proteins are key players in the V(D)J recombination process leading to the assembly of antigen receptor genes. Defects in RAG1/RAG2 genes are caused to different phenotypes of severe combined immunodeficiencies (SCID). Objective — to determine the clinical and laboratory manifestations in patients with RAG1 / RAG2 mutations from one single center, to identify the phenotype-genotype correlations. Materials and methods. We described 4 children with RAG1 mutations. Diagnosis of SCID was confirmed by criteria’s of European society of immunodeficiencies (ESID). Results. In two patients we observed Omenn syndrome, in 1 — classic T -B -NK + SCID, in 1 — «sof» T +B -NK + SCID. One patient with Omenn syndrome and patient with «soft» SCID had same RAG1 mutations. Conclusions. RAG 1 / RAG2 mutations are caused to severe life-threatening combined immunodeficiency, requiring radical therapy. We found no genotype-phenotype correlations in patients with RAG1 defects.