Chest wall diseases are characterized by an increased stiffness of the chest wall, and require more respiratory work to be done to ventilate the lungs adequately. We have reviewed the responses of the respiratory system for compensate for these mechanical loads: intrinsic (muscular) adaptation and central drive (extrinsic) adaptation. In ankylosing spondylitis, there is an efficient intrinsic adaptation, mostly by the diaphragm, with good respiratory prognosis. It is likely that eucapnic obese patients have a normal adaptation of respiratory drive, whereas the failure of the control of breathing may lead to obesity hypoventilation syndrome. In kyphoscoliosis, normal gas exchange is assumed by an increased muscular contribution, and so depends on an increased neural drive. However in major chest distortion, a failure of this neuromuscular compensation may occur and be responsible for life threatening episodes.