Objective: The cross-sectional area (CSA) and the volume of the pharyngeal airway normative reference data aren't established, although they are closely associated with the pathogenesis of obstructive sleep apnea syndrome (OSAS) in infants and preschool children. Our objective is to measure the cross-sectional area (CSA) and volume of pharyngeal airway subregions and investigate the effects of age and sex in infants and preschool children using computerized tomography (CT). Methods: After applying strict inclusion criteria, 57 infants and preschool children (27 females, 30 males) aged from 1 day to 72 months who underwent maxillofacial CT scans due to trauma were selected. The sample was stratified into three age groups (1 day-24 months, 25-48 months, and 49-72 months). The CSA and the volume of the naso-, palato-, glosso-, and laryngopharyngeal airway were calculated using a 3-dimensional image processing software. Linear regression analysis was performed to express the effect of age, height, and weight. One-way analysis of covariance with height as a covariate was used to analyze the statistical significance of the difference between males and females within each age group. Results: The CSA and volume of all pharyngeal airway subregions increased with age, height, and weight (P < 0.05) in children under 6 years old. Multiple linear regression analysis showed an age effect, identified in all measurements (P < 0.001), whereas no height or weight effect were found. There were no differences in any measurements between males and females within each age group. Conclusion: The normative reference data of CSA and volume of pharyngeal airway subregions were established after applying strict inclusion and exclusion criteria in infants and preschool children. Results may be useful in screening and assist in the timely diagnosis and management of pediatric OSAS.