Neonatal diabetes mellitus (NDM) develops within the first 6 months of life. It occurs with a frequency of 1 cases per 300,000 - 500,000 newborn infants. Pathogenesis of NDM involves over 10 different genes. Of greatest clinical significance are mutations in KCNJII and ABCC8 genes responsible for the activity of ATP-dependent potassium channels and regulating their activation. It was shown that the intake of oral sulfonylurea (SU) preparations results in the closure of these channels and thereby stimulates the release of insulin from beta-cells. For this reason, SU therapy can be applied as an alternative to insulin injections. SU preparations ensure the efficacious control of metabolic processes and substitute insulin in the majority of the cases of transient and permanent NDM associated with mutations in KCNJII and ABCC8 genes. The original observations demonstrating the relationship between the type of mutation in the KCNJII gene and the dose of SU preparations are presented.