This study was designed to analyze nasal respiratory patency and its correlation with skeletal components in growing children with anterior crossbite. The subjects consisted of 40 control patients, 24 nose breathers with anterior crossbite and 18 mouth breathers with anterior crossbite. The mean age was 11.4 years in the control group, 10.1 years in nose breathing group and 9.5 years in mouth breathing group. The results were as follows, 1. In anterior cross bite group, and nasal respiratory airflow rates (N.R.A.R.) was significantly lower than that of control group regardless of nasal decongestants application. 2. The N.R.A.R. of mouth breathers with anterior crossbite in male group was significantly lower than that of mouth breathers, but increased to the level of control group after nasal decongestants application. But in female group, the N.R.A.R. was significantly lower in mouth breathing group at both conditions. 3. Mouth breathing group showed smaller anterior vertical nasal cavity height (ANS-ANS´), lower upper anterior facial height ratios (N-sp´/N-Me) and higher maxillary occlusal plane ratios (OL-ML/ML-NL) than those of nose breathing group with anterior crossibte. 4. Items showing nasal height (ANS-ANS´, PNS-PNS´), anterior upper facial height (N-sp´) was were strongly correlated with N.R.A.R. at 150 pascal in inspiration. But item showing maxillary occlusal plane ratios (OL-ML/ML-NS) was negatively correlated with N.R.A.R. at 150 pascal in inspiration. 5. There were forward tongue position in mouth breathing group, but it was not significantly correlated with N.R.A.R. at 150 pascal in inspiration.