PURPOSE: The aim of this study was to compare the pharyngeal airway size in different cranio-cervical postures in children with sleep-disordered breathing (SDB) and asymptomatic control children. We tested the hypothesis that the site of the most constricted pharyngeal airway in SDB children is not affected by head posture. METHODS: The study group comprised 29 children (14 boys, 15 girls, mean age 7.3?±?1.37 years, range 4.8-9.8 years) with SDB. A control group of 29 age- and gender-matched healthy children was recruited. The pharyngeal airway of the children was imaged with a low-field 0.23-T open-configuration magnetic resonance imaging scanner in three different head postures: neutral, extension, and flexion. Inter-group differences in pharyngeal variables were analyzed using two-sided paired t test and intra-group differences using Bonferroni and Šidak correlations for multiple comparisons. RESULTS: Nasopharyngeal airway was not affected by head posture. Head extension had no significant effect on the most constricted retropalatal airway in the SDB group, but it increased the hypopharyngeal airway (P?=?0.000) significantly when compared to neutral head posture. The hypopharyngeal airway increased more in the SDB group than in the asymptomatic children (P?=?0.031). The retropalatal oropharynx was on the whole significantly narrower in the SDB children compared with the controls in all head postures (neutral P?=?0.000, extended P?=?0.001, flexed P?=?0.000). CONCLUSIONS: Head posture is an important factor in maintaining airway patency. We suggest that the effectiveness of neuromuscular compensation may be compromised in constricted retropalatal airways. Instead, the hypopharyngeal airway is enlarged suggesting possible neuromuscular compensation for oropharyngeal narrowing in children with SDB.