Object. The anatomy of the Guyon canal is crucial for open and endoscopic surgeries for ulnar canal syndrome at the wrist level. It is also of interest for surgical treatment of carpal canal syndromes. Whereas the Guyon canal is largely described in adults, no studies exist in children. In the present study, the authors examined the Guyon canal in children. Methods. Sectional anatomy was used. Thirty-two formalin-fixed cadavers (64 sides) were examined (age range 2-11 years). The hands were transversely cut into 2-3-mm-thick slices. Slices were placed in embedding medium, and transverse sections (10 mm thick) were stained with histological methods and photographed under a light microscope. Results. The roof of the Guyon canal was attached to the flexor retinaculum laterally to the hamulus of the hamate bone. Thus, the radial boundary of the Guyon canal was lateral to the hamulus, which became part of the floor of the Guyon canal. An ulnar neurovascular bundle was found directly volar to the hamulus in 93.8% of the cases and slightly medial to the hamulus (to the ulnar side) in 6.2% of the cases. Proximally, the ulnar artery and nerve were sustained by the flexor retinaculum in direct apposition to the carpal canal. Conclusions. In children, the Guyon canal displays an anatomical particularity regarding the topography of the ulnar artery and nerve that may be of relevance for intraoperative orientation and endoscopic navigation to avoid lesions to the ulnar nerve and artery in carpal and Guyon canal syndromes.73286289Anson, B.J., Maddock, W.G., (1958) Callander's Surgical Anatomy, ed 4, , Philadelphia: WB SaundersBozkurt, M.C., Tagil, S.M., Ozcakar, L., Ersoy, M., Tekdemir, I., Anatomical variations as potential risk factors for ulnar tunnel syndrome: A cadaveric study (2005) Clinical Anatomy, 18 (4), pp. 274-280. , DOI 10.1002/ca.20107Caetano, E.B., Brandi, S., Oliveira Jr., W.M., Ulnar nerve entrapment by a true aneurysm in Guyon's canal: Case report (2004) Rev Bras Ortop, 39, pp. 398-400Chiarugi, G., Bucciante, L., (1972) Istituzioni di Anatomia dell'Uomo, ed 10, , Milano: Casa Editrice Francesco VallardiCobb, T.K., Carmichael, S.W., Cooney, W.P., Guyon's canal revisited: An anatomic study of the carpal ulnar neurovascular space (1996) Journal of Hand Surgery, 21 (5), pp. 861-869. , DOI 10.1016/S0363-5023(96)80205-XCobb, T.K., Carmichael, S.W., Cooney, W.P., The ulnar neurovascular bundle at the wrist. 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