Three methods of evaluating the mode of breathing were applied in 119 children aged 7-15 years who were to start orthodontic treatment for various malocclusions. The three methods were: the history, rhinomanometric recording of the nasal airflow and determination of the size of the airway on profile and frontal cephalograms. The variables describing the mode of breathing were correlated with the facial morphology and the natural position of the head and the cervical spine as recorded with

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... e cephalometry. There were no correlations between the results of the evaluation of the mode of breathing obtained with the three methods. Nor were there any correlations between these and the position of the head or the cervical spine. A history of mouth-breathing, the rhinomanometrically determined airflow through the nose and the size of the airway on the profile cephalogram were, however, correlated with the long face morphology characteristic of mouth-breathing. A diagnosis of mouth-breathing should be based on different supplementary methods, the history and the size of the airway on the profile cephalogram being at least as valuable as the rhinomanometric recording.