However, the main aim of this study was to evaluate the selected NOS polymorphisms—rs3782218 (NOS1), rs1137933 (NOS2), rs1799983, rs2070744, and rs61722009 (NOS3)—as factors that may increase the risk of developing diabetic nephropathy or the increased likelihood of renal replacement therapy in patients with already developed diabetic nephropathy. This evidence concerns the gene NOS1 and diabetic kidney disease.