Lipoblastoma is a rare mesenchymal tumor, occuring in less than three-year-old infants in 90% of the cases and in 40% of the cases in chidren aged less than one year. It can be present at birth. It is a benign tumor, with defined margins, that can be locally aggressive, without metastases. We report the case of retroperitoneal lipoblastomatosis, with a neonatal diagnosis made by ultrasonographic and CT features.