BACKGROUND: The measurement of specific airway resistance during tidal breathing (sRaw(tb)) has gained popularity in children, but methodological concerns have been raised regarding the electronic compensation for the thermal artifact. The panting method (sRaw(p)) is efficient in minimizing the latter, but may be associated with a change in end expiratory lung volume if the effort is not properly balanced. The aim of the study was to compare sRaw(tb) with sRaw(p) in children. METHODS: Fifty-five children aged 6.5-11.5 years were studied. sRaw(tb) was measured in a commercial plethysmograph. sRaw(p) was measured with a home made equipment that allowed breath by breath analysis (sRaw(p1)) as well as with the commercial body box (sRaw(p2)). RESULTS: sRaw(tb) was significantly larger than either sRaw(p1) or sRaw(p2) (P < 0.0001). The mean (95% CI) difference sRaw(p1)  - sRaw(tb) was -0.374 (-0.835 to 0.088) kPa s. The difference between sRaw(p1) and sRaw(p2) was significant (P < 0.005) but not clinically relevant, and mean (95% CI) difference sRaw(p1) - sRaw(p2) was 0.115 (-0.094 to 0.324) kPa s. The breath by breath analysis showed small but significant increase in sRaw(p1) throughout the maneuver (P < 0.001), whatever the pattern of end expiratory level. CONCLUSION: Tidal breathing is associated with an overestimation of sRaw compared with panting in children. Although the latter results in small increase throughout the panting maneuver, sRaw(p) is probably more trustful than sRaw(tb).