We report a case of histopathologically confirmed benign lipoblastoma in the retroperitoneum. The tumor presented itself as an ill-defined low density mass on a simple radiograph, as a highly heterogeneous echogenicmass on US, and fatty density mass separated by unenhanced linear septa of soft tissue density on CT. The well circumscribed and encapsulated tumor was totally removed by operation. CT is considered the modality of choice for characterizing lipoblastoma and demonstrating its location and boundary. When there is fatty density mass in there troperitoneum of a children, the possibility of lipoblastoma should be considered first.