The author experienced a case of lingual thyroid. The patient, 11-year-old girl, was seen with chief complaints of nasal obstruction and nasal mucopurulent discharge. On physical examination the nasal cavity showed mucopurulent discharge in the both middle meatus, and oral cavity revealed a tumor mass on the basis of the tongue, 2×1cm in size, slightly elevated with bluish red in color. Suspecting lingual thyroid, scintigram was done, which revealed a functioning thyroid on the posterior tongue region, measuring 3×2.5cm concentrated by RI¹³¹ and no concentration of RI¹³¹ in the neck. There was no any symptoms and signs due to the tumor, therefore no treatment was given for it.