Pectus deformities are among the most common anterior chest wall pathologies. Pectus excavatum is the most common chest deformity with an incidence of 0.1-0.3%. In severe deformities, a decrease in lung volume is observed. This can cause decreased pulmonary function and affect the function of the right ventricle. The diaphragm is the main respiratory muscle, and diaphragm contraction is associated with respiratory functions. So, investigators aimed to measure diaphragmatic thickness in adolescents with pectus deformity and to show whether diaphragmatic thickness is an early predictor of respiratory disorder in participants who do not show any clinical symptoms or whose respiratory functions are normal.