The case represents a newly diagnosed non-small cell lung cancer (squamous cell carcinoma) by bronchoscopy and requested for baseline CT study, and showing the above-mentioned finding of left upper lobe lung collapse due to cancer bronchus and the case also demonstrates luftsichel sign due to the hyperexpanded superior segment of the left lower lobe, which insinuates itself between the left upper lobe and the superior mediastinum, sharply silhouetting the aortic arch and resulting in a lucency medially.