In 50 female patients (age: 16.2 + 5.1 years) with idiopathic scoliosis (COBB: 67 ± 21°) 40 variables of lung function and spiroergometry as well as of scoliosis were investigated by means of factor analysis, Nine factors were found the variables of which correlated significantly with each other also after eliminating the influence of all other variables. The relations between the first three factors were not plausible and therefore they were not subjected to interpretation. Another three factors yielded relations well known in the field of clinical respiratory physiology and sport medicine, e. g. the positive correlation between arterial pO2 during physical work and pulmonary diffusion capacity, or the negative correlation between resting heart rate and maximal aerobic capacity. In the last three factors essential new results were found: (1) The maximal aerobic capacity does not correlate with the reduced actual values for vital capacity or total capacity but with the antropometric data. (2) There is no causal dependence between the degree of scoliosis and any of the lung function or spiroergometric parameters.Conclusions: (1) From the degree of scoliosis one cannot draw conclusions about the quality of lung function. The often described significance of the negative, direct, single linear correlation between degrees Cobb and vital capacity may be interpreted only as an expression of simultaneity, not of causality. (2) In spite of the often abnormal mechanics of thorax and lungs, the respiration in scoliotic patients, functions as in healthy subjects considering the oxygenization of the blood and the supply of O2 to the organism during rest and exercise. Therefore, a reduced aerobic capacity is not the consequence of scoliosis in most patients, but the consequence of keeping away the patients from school sports and other sport activities. This leads to a chronic lack of physical training and a bad physical state of respiration, circulation and aerobic muscle metabolis