Lung cancer is the most prevalent malignancy in the world. The number of new cases of lung cancer worldwide can reach 1 million every year and is growing at a rate of 0.5% per year. The situation in China is not optimistic either. The latest warning issued by the National Cancer Control Office of the Ministry of Health in the “National Cancer Control Strategy Study Report”: “Lung cancer is the number one cancer in China”. It is predicted that in 2005, there will be 330,000 men and 170,000 women with lung cancer in China. Clinical practice shows that about 80% of lung cancer patients are already in advanced stage when first diagnosed, which makes the overall effect of lung cancer treatment still unsatisfactory. According to statistics, the overall 5-year survival rate of lung cancer in China is 8-14%, while the 5-year survival rate of early-stage lung cancer patients can reach 80%-85% after treatment. Therefore, it is doubly significant to improve the understanding of lung cancer, early or timely detection, early diagnosis, avoiding misdiagnosis and early treatment to improve patients’ prognosis and increase social benefits. To fully understand the characteristics of lung cancer and prevent misdiagnosis from both doctors and patients is the key to achieve early detection, early diagnosis and early treatment. First, regular physical examination is emphasized. About nearly half of the early stage lung cancer has no symptoms, which is an important reason why lung cancer patients cannot be detected early. For high-risk groups (men aged ≥45 years old and smokers ≥400 years), X-ray and sputum cytology examination should be performed every six months. Secondly, the clinical symptoms of lung cancer are non-specific and can be manifested as cough, sputum, chest pain, shortness of breath and other symptoms of general respiratory diseases. Many patients have a history of smoking and may combine with chronic bronchitis and obstructive emphysema, which may also have the above symptoms and conceal the disease. Therefore, such patients should be alerted and seek medical attention promptly if they experience worsening cough symptoms or irritating dry cough, blood in sputum or intractable chest pain. In addition, the symptoms of lung cancer patients may temporarily improve or disappear after anti-inflammatory treatment, so they may be easily mistaken as general “cold”, and without further examination, the condition may be delayed. Isolated or one-sided view of lung lesions found on imaging can lead to misdiagnosis of lung cancer. There is an inevitable and complex connection between pulmonary lesions and pulmonary imaging manifestations, but the same pathological changes can produce different imaging manifestations, while different pathological changes can produce similar imaging manifestations, so a comprehensive analysis should be made in conjunction with the disease, among which special attention should be paid to the differential diagnosis with pulmonary tuberculosis. For patients with years of history of quiescent tuberculosis who have reached cancer-prone age, when symptoms such as cough, chest pain and hemoptysis appear again, the possibility of cancer should be noted, and at this time, multiple examinations and repeated comparison with original X-ray films should be used, which can help in diagnosis. Meanwhile, clinical examples of lung cancer co-existing with tuberculosis have been found. Those whose symptoms do not improve significantly during anti-tuberculosis treatment or whose X-rays show an increase in lesions should be considered as possible lung cancer. In addition, the diagnosis cannot be confirmed solely by the tuberculin test (PPD). a positive PPD test result indicates that the patient is infected with tuberculosis, but when the organism is less reactive, the PPD can be negative. There is also a case when cancer cells are not detected and the patient is reluctant to undergo surgical treatment causing a delay in the disease. It is common to find patients with isolated pulmonary nodules who are “afraid of surgery” and choose to be observed because the pathology cannot be defined preoperatively, but the observation time is too long, causing delays. Clinical experience is that about 60-70% of isolated pulmonary nodules >2 cm in diameter are malignant, and 90% of those >3 cm in diameter are malignant. Our strategy for patients with isolated pulmonary nodules is to review chest CT after 2 weeks of anti-infection and anti-TB treatment, and to take surgical treatment if the lesion increases or does not shrink, even if the patient requests continued observation and follow-up, the time should not exceed 1 month. Finally, lung cancer can secrete hormone-like substances (ectopic endocrine) causing complex syndromes with cancer and extra-pulmonary symptoms, such as hypercalcemia, Cushing′s syndrome, hyponatremia, neuropathy and hypertrophic osteoarthropathy.