CT of the lung cannot exclude lung cancer. CT of the lung is mainly used to detect occupying lung lesions, ground glass shadows, soft tissue density masses or multiple lung tumors or nodule-like changes. CT can only provide imaging characteristics and CT values are for clinical reference only, but the specific nature of the lesion can only be clarified by the above pathological examination. Tuberculosis mostly appears as ground glass-like shadow, and anti-tuberculosis treatment is effective, while lung cancer appears as soft tissue mass with unclear boundary and uneven density, and CT value is around 60-80HU, so lung cancer cannot be excluded by CT.