Hyperinflation of the laryngeal mask airway cuff may exert high pressure on pharyngeal and laryngeal structures. In vitro data show that high intra cuff pressures may occur when inflated to only 30% of the manufacturer’s recommended maximum inflation volume. We prospectively assessed the pressure volume curves of paediatric sized laryngeal mask airways (size 1–3) in 240 consecutive children (0–15 years). Following laryngeal mask airway insertion the cuff was inflated with 1-ml increments of air up to the maximum recommended by the manufacturer. After each ml cuff pressure was measured. At the end all cuff pressures were adjusted to 55 cmH2O. The maximum recommended volume resulted in high intracuff pressures in all laryngeal mask airway brands and sizes studied. Approximately half the maximum volume produced a cuff pressure ≥ 60 cmH2O. This occurred in all brands and all sizes studied. We recommend that cuff manometers should be used to guide inflation in paediatric laryngeal mask airways.