OBJECTIVE: To present the case of a child with neonatal primary hyperparathyroidism submitted to preoperative image studies that couldn't localize the parathyroid glands. METHODS: Report of clinical and laboratory evaluation of neonatal primary hyperparathyroidism in a two-and-a-half-monthold child submitted to preoperative cervical ultrasonography and parathyroid scintigraphy with Technetium-99m-Sestamibi, and subtotal parathyroidectomy at the age of four-and-a -half months. RESULTS: The preoperative images suggested an erroneous diagnosis of parathyroid adenoma. After surgery and pos-operative histopathological exams, hyperplasia of parathyroid glands was confirmed. After two years and a half the child has normal parathyroid function. CONCLUSIONS: The cervical ultrasonography and the parathyroid scintigraphy with Technetium-99m-Sestamibi were not useful for preoperative localization of hyperplasied parathyroid glands in the neonatal primary hyperparathyroidism in this case. The subtotal parathyroidectomy has been a successful method for the maintenance of normocalcemy in the patient.