The sign has been originally described on chest radiographs. It is formed by distorted blood vessel(s) and a focal area of atelectatic lung adjacent to pleural thickening. The vessel(s) are seen as curvilinear soft tissue density or densities, extending from the medial margin of the atelectatic lung to the pulmonary hilum. When the vessels are multiple thus there are multiple tails, the vessels are more likely parachute; then, parachute sign may be used (Fig. 5.1). The sign is due to contracted fibrous scarring and shrinking pleural disease with rounded atelectasis. Likewise, on CT, swirling of bronchi and vessels extending from the hilum and converging on the atelectatic lung help produce comet tail appearance [1] (Figs. 5.1 and 5.2).