Computed Tomography (CT) and Magnetic Resonance (MR) permit the acquirement of important diagnostic elements for the anatomo-topographic staging of substernal goiters, and for their characterization. The authors compared data obtained by CT and MR with intraoperative anatomo-topographic findings and definitive histology in 28 patients with substernal goiters. CT was performed in all these patients while MR only in 9. The results obtained showed an accuracy of 85.7% for CT and 100% for MR regarding the anatomo-topographic correspondence with intraoperative findings, without a significant statistical difference between these two diagnostic procedures. MR is more accurate than CT in showing the vascular dislocations. CT and MR have an accuracy of 82.1% and 77.7% respectively comparing their findings with histologic results obtained in operative specimens, without a significant statistical difference. In conclusion MR has to be considered the more accurate diagnostic procedure and therefore recommended in the study of patients with substernal goiters, while CT can be performed only in selected patients.