PURPOSE: Leiomyoma is a rare benign tumor of nonstriated muscles. Leiomyoma is most commonly found in the uterus or rarely occur in the hand. 150 cases of leiomyoma of the hand have been reported in the English literature; however, to the best of our knowledge only four of these have been in children and none were reported in Korean literature. We present a case of leiomyoma in the hand of a 8-year-old boy, which is a rare site for localization and unusual for age. METHODS: A 8-year-old boy presented with a painless mass on the ulnar side of his thumb. Physical examination revealed a 1.2x1.2cm round, rubbery mass that was nontender to palpation. The vascular, sensory, and motor exams were otherwise unremarkable. Further evaluation with CT demonstrated an enhancing mass at dorsoulnar aspect of 1st proximal phalangeal region suggestive of a hemangioma versus other enhancing solid mass. The diagnosis of a leiomyoma was confirmed following surgical excision with histologic evaluation. RESULTS: In 3 months follow-up, the incision was healed, motor and sensory function were intact, and full range of motion was recovered. Neither recurrence nor postoperative complication were observed. CONCLUSION: Leiomyoma is a rare tumor of the hand, especially in children. Diagnosing hand tumors in children is more difficult than in adults, hand surgeons should be aware of the diagnostic possibilities based on examination and imaging of a hand tumor; however, surgical excision with histologic examination is required for definitive diagnosis.