The purpose of this study was to compare the cardiorespiratory responses during treadmill exercise in 19 children (age, 10.5 ± 1.6 years) wearing a facemask and sealant versus a mouthpiece and nose clip. Cardiorespiratory responses were measured at 80.4 m · min−1, 134.0 m · min−1 and at peak exercise during two separate exercise tests. During the facemask trial, VO2 (ml · kg−1 min−1) was 16.9 ±3.1 at 80.4 m · min−1, 36.2 ± 3.9 at 134.0 m · min−1, and 49.5 ± 5.6 at peak exercise. During the mouthpiece trial, VO2 was 17.2 ± 2.8,36.7 ± 3.9, and 49.9 ± 5.2, respectively. VE (L · min−1) at the three intensities were 13.6 ± 2.2, 34.3 ± 5.7, and 56.5 ±11.1 for the facemask trial and 13.2 ± 1.6, 33.4 ± 5.0, and 54.8 ± 11.9 for the mouthpiece trial, respectively. Differences between trials were not significant. Intraclass correlations between the trials for VO2, (ml · kg −1 · min−1) ranged from R = 0.83 while walking to R = 0.95 at peak exercise; for VE, the intraclass correlations ranged from R = 0,63 to R = 0.91. In conclusion, die use of a facemask and sealant during exercise testing in this age group produced comparable results to those obtained using a mouthpiece and nose clip, and was more preferred.