Based on age-dependent differences in pulmonary mechanics, the effect of neuromuscular blockade may differ in infants compared with older children. The aim of this study was to determine the impact of neuromuscular blockade and its reversal by positive end-expiratory pressure (PEEP) on functional residual capacity (FRC) and ventilation distribution in young infants and preschool children. ⋯ Although the use of neuromuscular blockade decreased FRC and ventilation distribution substantially in both groups, the changes were more pronounced in young infants. With PEEP, FRC increased and ventilation homogeneity was restored. These results provide a rationale to use PEEP in anesthetized, paralyzed infants and children.