Basically malignant tumors in the retroperitoneal region arise from a heterogeneous group of tissues: mesodermal, neurogenic, germ cell, and lymphoid. Although rare, benign tumors and cystic masses can be also encountered in retroperitoneal space. Developments in computed tomography (CT) and magnetic resonance imaging (MRI) have contributed to both diagnosis and staging of the retroperitoneal tumors. High spatial resolution and superiority in calcification make CT indispensable; on the other hand, MRI has a better soft-tissue contrast resolution which is essential for the assessment of vascular invasion and tissue characterization. The aim of this article is to review the CT and MRI features of retroperitoneal tumors and their subsequent management.