Previous clinical experience in the study of the soft tissues of the neck region has pointed out the accuracy of MRI in terms of high definition and contrast resolution. Seventy-seven patients with thyroid diseases were examined to define the possible role of MRI in the diagnosis of these conditions. In the patients affected with thyroiditis, MR findings were not specific, showing increased glandular volume and signal inhomogeneity. MR examinations of struma allowed an accurate evaluation of glandular size; furthermore, more information was obtained than with other imaging modalities in the cases with mediastinal involvement. On T2-weighted images, adenomas were always hyperintense, whereas variable signal intensity was seen on T1-weighted scans, with the exception of Hürthle cell adenomas, which were hyperintense on both T1- and T2-weighted sequences. MRI proved to be reliable in the depiction of tumor spread at both glandular and extraglandular levels. The distinction between scar fibrosis and relapse was also possible, in the cases undergoing postoperative follow-up. In conclusion, MRI emerges as a diagnostic tool complementary to other imaging techniques. However, in selected conditions--e.g., mediastinal struma and tumors--and in the postoperative follow-up, MRI can be considered the method of choice.