Objective To analyze the anatomical characteristics of the upper airway in Pierre Robin sequence pediatric patients with difficult laryngoscopy using the computed tomography-based three-dimensional reconstruction.Methods Fifty pediatric patients of both sexes with Pierre Robin sequence,aged 10-101 days,weighing 2.0-6.3 kg,of American Society of Anesthesiologists physical status Ⅲ,scheduled for elective mandibular distraction osteogenesis under general anesthesia,were enrolled in this study.Cone beam CT scan was performed to obtain upper airway anatomy information during the natural sleep before operation.Images were imported into medical engineering software MIMICS 17.0 to reconstruct the three-dimensional images of the oral and maxillofacial bones and airways.The related anatomical parameters were measured,including the distance between the alveolar ridge of the upper central incisor and root of the epiglottis (D1),distance between the root of the epiglottis and midpoint of glottis (D2),distance between the bilateral lower edge of the mandible and midpoint of glottis (D3),distance between the alveolar ridge of the lower central incisor and the lower edge of the mandible (D4),length of the mandibular ramus (D5),length of the mandible body (D6),and length of the total mandible (D7),angle between lines D1 and D2 (angle 1),the angle between line D2 and the alveolar ridge of the upper central incisor to the midpoint of glottis (angle 2),the angle between lines D3 and D4 (angle 3),the angle of the point of the upper central incisor alveolar ridge to the trailing edge of the hard palate and then to the root of epiglottis (angle 4),the angle of bilateral mandible (angle 5),the angle of the point of gnathion to the two gonions (angle 6),the airway cross-sectional area at the tip of epiglottis,volume of oral cavity,volume of velopharyngeal cavity,and volume of glossopharyngeal cavity.Fiberoptic bronchoscope-guided endotracheal intubation was performed under topical anesthesia with lidocaine.Propofol,sufentanil and cis-atracurium were intravenously injected to induce anesthesia after successful intubation,and then the pediatric patients were sent to the operating room.Anesthesia was maintained by inhalation of sevoflurane.The exposure of glottis was observed with a laryngoscope.Pediatric patients were divided into difficult laryngoscopy group (group A) and non-difficult laryngoscopy group (group B) according to whether they presented with difficult laryngoscopy (Cormack-Lehane classification Ⅲ or Ⅳ).Results Compared with group B,the airway cross-sectional area at the tip of epiglottis and in the volume of velopharyngeal cavity were decreased (P＜0.05),and no significant change was found in D1,D2,D3,D4,D5,D6,D7,angle 1,angle 2,angle 3,angle 4,angle 5,angle 6,volume of oral cavity or volume of glossopharyngeal cavity in group A (P＞0.05).Conclusion The three-dimensional CT images of the upper airway show characteristic changes in Pierre Robin sequence pediatric patients with difficult laryngoscopy,and the main manifestations are the decrease in the airway section area and in the volume of the palatopharyngeal cavity at the tip of the epiglottis.