Nine hundred and forty-six cases of primary immunodeficiency diseases were diagnosed in the Department of Immunology of the Children’s Memorial Health Institute in Warsaw during 1980-2006. The highest frequency was that of antibody immunodeficiencies: 547 (57.8%). Predominantly T cell deficiencies were recognised in 80 (8.5%) children. In 29 children severe combined immunodeficiencies with different genetic defects were diagnosed, and in 18 of them hematopoietic stem cell transplantation was done. In the group of phagocytic disorders (95; 10% of patients), neutropenia was the most common - 46 cases, followed by chronic granulomatous diseased recognised in 41 patients. In the group of other well-defined PIDs - immunodeficiencies associated with chromosomal instability were the most common (152; 16% of patients). Ataxia – teleangiectasia was diagnosed in 92 cases and, next, Nijmegen Breakage syndrome in 57 children. Hyper IgE syndrome was diagnosed in 22 patients, and Wiskott-Aldrich syndrome in 19 boys.