A sixteen-years-old female was referred to the Department of Otorhinolaryngology, Tartu University Clinics, for asymptomatic tumorous enlargement of the tongue base. By using CT, radionucleide imaging and histological examination, the lingual thyroid was diagnosed. In literature, the prevalence of such condition has been estimated as low as 1 case per 100000 persons. Its true estimations is difficult due to the usually asymptomatic disease course. The most precise diagnostic technique to preoperatively establish the location of the ectopic thyroid gland is radionucleide imaging using Tc – 99m sodium pertechnetate.