Castleman disease is a relatively rare disease of differential diagnostic interest in patients with lymphadenophathy. The etiology and pathogenesis of the Castleman disease studied by MRI are presented : one case presented with a localized anterior mediastinal mass and the other case, with a neck mass. The lesions were characterized by relatively high signal intensities on both T1 and T2 weighted images in both cases, and singificant degree of enhancement was seen in the cervical Castleman disease.