Two parameters of tidal breathing, the ratio of time to reach peak tidal expiratory flow to the total expiratory time (Tme/TE) and the ratio of volume exhaled at peak tidal expiratory flow to the total exhaled volume (dV/VT) were used to assess lung function in 21 sedated infants (aged 6–14 mo) with different degrees of airway obstruction. These parameters were compared with airway resistance as percentage predicted (Raw%) and maximum expiratory flow at functional residual capacity corrected for lung volume (VmaxFRC/TGV) VmaxFRC/TGV values correlated significantly with Tme/TE (r= 0.630,p= 0.002) as well as with dV/VT (r= 0.728.p- 0.001). Raw% values showed only a weak correlation with dV/VT (r- - 0.435,p- 0.048). We conclude that Tme/Te and dV/VT are both able to detect airway obstruction in infants and that these parameters corrclate much better with the forced expiratory flow values obtained by the rapid thoracic compression method than with airway resistance, determined by body plethysmography.