Background: Nesidioblastosis is often resistant to medical therapy and requires near-total pancreatectomy. There is little information on the postoperative imaging findings of these patients. Objective: To demonstrate by US the late imaging findings in these patients. Materials and methods: Children diagnosed with nesidioblastosis and who had undergone 90–95% pancreatectomy received preoperative, immediate-postoperative (within 10 days of surgery) and long-term annual US examinations. In the preoperative study, three anterior–posterior (AP) measurements were obtained of the head, body and tail of the pancreas. In the postoperative and long-term follow-up US, AP and transverse measurements of the pancreatic remnant were obtained. Pancreatic echogenicity was also assessed. The results were compared with normal pancreatic dimensions as a function of age. Glucose metabolism and pancreatic enzymes were also analysed. Results: The study group comprised 22 patients (aged 9 days to 2 years). The pancreas was normal in all preoperative US examinations. The first postoperative examination showed, in all patients, a remnant of the pancreatic head measuring 8–13 mm. The last follow-up US was similar to the first postoperative study in 6 patients, and 12 showed complete pancreatic regeneration (normal size, echogenicity and function), and 4 had incomplete regeneration with head and body normal in size, but lack of a pancreatic tail. All patients were asymptomatic and showed normal laboratory tests. Conclusions: US measurements indicated normal age-dependent growth after near-total resection in 54% of patients. The function and echogenicity of the regenerated pancreas indicate that the increase in organ size was due to normal pancreatic tissue.