Morphological changes that occur during various lung diseases have been evaluated by CT. However, static CT images at full inspiration reflect only a single phase of the respiratory cycle and the pathological changes in the lung are sometimes difficult to detect. To overcome this limitation, respiratory dynamic, or paired inspiratory and expiratory images of diseased lungs have been obtained using spiral or ultrafast CT. This technique can directly assess not only tumor invasion of the chest wall but also regional lung function such as air tapping or abnormal lung compliance. In addition, fact CT also allows regional pulmonary blood flow to be assessed by analyzing the time-attenuation curve after a contrast injection. This article reviews recent  progress of chest CT diagnosis, and focuses upon the dynamic evaluation of various  pulmonary diseases.