Both a laryngeal web and thyroid cartilage anomaly are rare airway abnormalities and can cause the obliteration of the tracheal diameter, which may be asymptomatic or symptomatic. In asymptomatic patients, the presence of unsuspected obliteration of the tracheal diameter may be problematic if endotracheal intubation is indicated. We report a case of unsuspected difficult intubation caused by a combined laryngeal web and congenital anomaly of the thyroid cartilage. A 14-year-old female was scheduled for corrective surgery for idiopathic scoliosis of the spine. After injection of IV induction agent and muscle relaxant, most of the vocal cords were exposed clearly by laryngoscopy, but a 6.0 mm internal diameter (ID) endotracheal tube could not be advanced below the level of the vocal cords because of resistance. Intubation was re-attempted with smaller tube (5.0 mm ID) only to fail. We awakened the patient and consulted an otolaryngologist. An Otolaryngologic examination and radiologic study revealed the narrowing of the trachea was caused by a laryngeal web and congenital anomaly of the thyroid cartilage. Later, a tracheotomy was performed under local anesthesia and then the laryngeal web and anomalous portion of the thyroid cartilage were removed under general anesthesia.