OBJECTIVE To determine the effect of prone positioning on ventilation distribution in children with acute respiratory distress syndrome. METHODS Prospective observational study. METHODS Paediatric Intensive Care at Red Cross War Memorial Children's Hospital, Cape Town, South Africa. METHODS Mechanically ventilated children with acute respiratory distress syndrome. METHODS Electrical impedance tomography measures were taken in the supine position, after which the child was turned into the prone position, and subsequent electrical impedance tomography measurements were taken. RESULTS Thoracic electrical impedance tomography measures were taken at baseline and after 5, 20, and 60 minutes in the prone position. The proportion of ventilation, regional filling characteristics, and global inhomogeneity index were calculated for the ventral and dorsal lung regions. Arterial blood gas measurements were taken before and after the intervention. A responder was defined as having an improvement of more than 10% in the oxygenation index after 60 minutes in prone position. Twelve children (nine male, 65%) were studied. Four children were responders, three were nonresponders, and five showed no change to prone positioning. Ventilation in ventral and dorsal lung regions was no different in the supine or prone positions between response groups. The proportion of ventilation in the dorsal lung increased from 49% to 57% in responders, while it became more equal between ventral and dorsal lung regions in the prone position in nonresponders. Responders showed greater improvements in ventilation homogeneity with R improving from 0.86 ± 0.24 to 0.98 ± 0.02 in the ventral lung and 0.91 ± 0.15 to 0.99 ± 0.01 in the dorsal lung region with time in the prone position. CONCLUSIONS The response to prone position was variable in children with acute respiratory distress syndrome. Prone positioning improves homogeneity of ventilation and may result in recruitment of the dorsal lung regions.