Congenital hyperinsulinism (CHI) is a rare and heterogeneous disease with a challenging diagnostic process and a need of individualised treatment of each patient. In severe, neonatal or infant CHI, differentiation between the focal and diffuse form by rapid genetics, 18F-fluoro-L-dihydroxyphenylalanine positron emission tomography/computed tomography and peroperative microscopy of frozen section allows surgeons to resect the focal lesion instead of performing subtotal pancreatectomy. Milder CHI, sometimes difficult to diagnose, is treated conservatively. In spite of all improvements, cerebral complications are still frequently seen.