Klippel-Feil syndrome is a rare disease with congenital musculoskeletal condition characterized by faulty segmentation of cervical vertebrae and consists of cervical vertebra fusions with limitation of head movements, short neck and low posterior hairline. In several cases the syndrome is associated with cardiovascular malformations. Patients affected by Klippel-Feil syndrome could be an anesthetic challenge, not only during cardiac surgery. We are presenting a case of Klippel-Feil Syndrome in an adult patient, who was operated on for a pulmonary valve insufficiency in a previously corrected Tetralogy of Fallot Syndrome. We are going to discuss the features of this rare syndrome