Background: Type 1 diabetes mellitus is the most common chronic metabolic condition in children that may occur at any age, with a more rapid increase in incidence in younger children (ages < 2 years). Diabetes diagnosed <6 months of age (NDM) is likely to have a monogenic cause. Methods: Our study was conducted on 94 pediatric patients with DM divided into 2 groups, a study group that included 54 patients (< 2 yrs at the onset), and 40 patients (> 5 yrs at the onset) as controls. Cases in our study were divided into 2 groups, 1st group with neonatal diabetes (onset in the 1st 6 mo) and the 2nd group (onset 6 mo - 2 yrs). Patients in both groups as well as controls were studied and compared regarding their perinatal, family and disease history, investigated for possible aetiology and genetic susceptibility for diabetes and followed over 1 yr period to evaluate their therapy and their glycemic control. Results: Patients with neonatal diabetes included monogenic and type 1 DM. In 10 cases with NDM, 3 cases were transient (TNDM) and 7 had permanent NDM (3 had KCNJ11 mutation, 2 had INS mutation & 2 had no mutations). DKA and neurological manifestations were more common in infantile diabetes compared to diabetic controls presenting at older age (p = 0.0001 & 0.001 respectively). Basal insulin regimen (+ bolus) was satisfactory for glycemic control in 73.9% of cases with infantile onset diabetes compared to controls (p = 0.02). Conclusions: Molecular genetic diagnosis should be established in all cases with NDM as it may affect course and treatment as cases with NDM with Kir 6.2 mutations were treated successfully with oral sulfonylureas.