Objective To study the application of PET/CT in lung cancer with different pathological types (squamous cell carcinoma, adenocarcinoma, small cell lung cancer). Methods A total of 198 patients with lung cancer from January 2016 to January 2018 were studied. According to the standard of operation and pathology, the characteristics and accuracy of different types of lung cancer were examined by PET/CT. Results The pathological examination of squamous cell carcinoma, adenocarcinoma and small cell lung cancer were 80 cases (40.0%), 70 cases (35.4%) and 48 cases (24.2%) respectively. And 80 cases (40.0%) of squamous cell carcinoma, 69 cases (34.8%) of adenocarcinoma and 46 cases (23.2%) of small cell lung cancer were performed by PET/CT, respectively. The accuracy rate was 98.5%. The PET/CT features of squamous cell carcinoma were as follows: high density mass located at the upper lobe of lung, with clear boundary, superficial lobes and pleural adhesion, and pleural indentation was seen. PET showed that the radioactivity uptake was increased with the average SUVmax was 30.6. The PET/ CT findings of adenocarcinoma included that the mass located at the upper lobe of the lung, with unclear boundary, and irregular shape, PET showed that the uptake of PET/ CT was increased with the mean SUVmax was 12.1, The PET/CT findings of small cell lung cancer including that a increased density mass located in hilum and mediastinum, with the uptake of PET/CT increased and the mean SUVmax was 9.5. Conclusion The PET/CT findings of lung cancer helps to the diagnosis of pathological types (squamous cell carcinoma, adenocarcinoma and small cell lung cancer) . The PET/CT findings of the lung cancer with different pathological types are obviously different.