BACKGROUND Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycemia in infants. Its management can be extremely complicated, and may involve medical therapy and surgery. The mainstay of the treatment is to maintain normoglycemia, since hypoglycemia during infancy can have severe neurological consequences. OBJECTIVE To assess the cognitive and developmental levels and the adaptive skills achieved by children with CHI who were treated medically over the past decade. METHODS Fourteen children with CHI, under the age of 10 years, who received medical treatment only, underwent a physical and neurological examination and standardized assessments that included the Bayley Scale of Infant and Toddler Development, 3rd Edition, or Kaufman Assessment Battery for Children, the Vineland Adaptive Behavior Scales and the Achenbach Child Behavior Checklist (CBCL) parent questionnaire form. RESULTS Twelve children (86%) achieved normal range scores in the cognitive and development assessments (Bayley Scale of Infant and Toddler Development or Kaufman Assessment Battery for Children). Only two showed cognitive achievements below the normal range. The Vineland questionnaire, which was based on parental report, showed below normal adaptive skills in eight patients (57%). CONCLUSIONS In contrast to previous studies showing a high prevalence of neurodevelopmental difficulties in children with congenital hyperinsulinism, our study showed normal cognitive achievements in most children. This may be attributed to the earlier recognition and better management of the disease in the past decade.