Introduction Accessory thyroid is defined as the presence of thyroid tissue in locations other than the normal anterior neck region between the second and fourth tracheal cartilages. It is a congenital disease caused by the abnormal migration of thyroid tissue in the embryonic stage. Lingual thyroid is the most common form of ectopic thyroid, extra lingual thyroid tissue is commonly located in the anterior cervical area, along the path of the thyroglossal duct. Case report Through a review of 2 different cases, the etiopathogenetic, clinical-diagnostic, and therapeutic aspects of ectopic thyroid tissue are here in discussed to highlight the main presentations of this polymorphous disease. The first case involved an ectopic thyroid gland in the submandibular region with no normally positioned thyroid in a male child of 9 years old with congenital hypothyroidism without mental retardation. The child was put on thyroid hormone treatment and the thyroid hormone level was restored. The second case involved a 40-year-old woman, presenting 3 months after total thyroidectomy, two right lateral cervical masses with moderate signs of compression and without signs of inflammation or thyroid dysfunction. The Cervical tomodensitometry revealed the presence of three tissue formations above the hyoid bone 7.6 × 7 mm, pre hyoid 16 × 12 mm and para hyoid 40 × 31.5 mm compatible with accessory thyroid with empty thyroid lodge. Conclusion The ectopic thyroid is classified under the category of congenital hypothyroidism, and it is one of the top causes of thyroid dysgenesis. The first case illustrate the importance of newborn screening and identification of congenital hypothyroidism which is the commonest treatable cause of mental retardation. Key-Words Ectopic –Accessory-Thyroid-Hypothyroidism