Prediction of ventilation weaning outcome in children is important, as unsuccessful extubation increases both morbidity and mortality. Adult weaning criteria are poor predictors of weaning outcome in children for several possible reasons: the length of mechanical ventilation is generally much shorter, and the weaning failure rate is lower in children (thus larger patient numbers are required); integrated weaning indices, such as the rapid shallow breathing index, do not account for normal developmental changes in respiratory function; and the heterogeneity of mechanically ventilated children is greater than in adults. The challenge remains to find universal weaning outcome predictors in children.