Abstract: Objective To explore the diagnostic value of multi-slice spiral CT in the patients with non-small cell lung cancer or small cell lung cancer. Methods A total of 86 patients with suspected lung cancer were given CT examinations, and the CT signs of pathologically confirmed non-small cell lung cancer and small cell lung cancer were observed. Meanwhile, the diagnostic sensitivity, specificity and accuracy of multi-slice spiral CT were calculated with pathological biopsy as the “gold standard”. Results There were 79 cases of lung cancer, 3 cases of pulmonary tuberculosis and 4 cases of pulmonary fibroma confirmed by gold standard, including 49 cases of non-small cell lung cancer and 30 cases of small cell lung cancer. Multi-slice spiral CT showed there were 75 cases of lung cancer including 72 confirmed cases. The diagnostic sensitivity, specificity and accuracy were 91.14%, 57.14% and 88.37%, respectively. The CT signs of the two types of lung cancer were statistically significant in terms of round, central, bronchial occlusion, atelectasis/obstructive pneumonia, mediastinal lymph node fusion and mediastinal vascular invasion(P<0.05). Conclusion CT signs of non-small cell lung cancer and small cell lung cancer are different to some extent, and can provide basis for clinical diagnosis.