Ectopic cervical thymic tumor, first described in 1941 by Boman, is a rare tumor of the neck displaying the same histologic features as mediastinal thymoma. It was classified into benign thymoma, invasive (or malignant) thymoma, thymic carcinoma histopathologically and clinically. The ectopic cervical thymic tumor is misdianosed as the thyroidal mass on radiologic examination and FNA cytology due to its rarity and unusual location. Recently, we have experienced two cases of ectopic cervical thymic tumor misdiagnosed as thyroid mass ; a case of thymic carcinoma;the other of invasive thymoma. So, we report these cases with review of the literature.