Lung cancer screening has been a controversial issue for many years, including the low-dose spiral CT, which is considered the most promising screening tool for lung cancer. The ability of CT screening to reduce lung cancer mortality has been debated internationally. In the 1970s and 1980s, the National Cancer Institute initiated several randomized subgroup trials of lung cancer screening with X-ray chest radiographs and sputum cytology, which showed that although more early-stage lung cancers were detected and postoperative survival was prolonged in those detected early-stage cases, the frequency of advanced lung cancers and the number of lung cancer deaths did not decrease through follow-up. This series of results leads to the thought that the improvement in survival is due to the fact that low-dose spiral CT screening detects cases that are slow-growing or “inert lung cancers” that pose relatively little threat to one’s health and do not progress rapidly to advanced stages and cause death. The Mayo Lung Cancer Study in the United States has confirmed that some lung cancers are not very dangerous. In this randomized, controlled lung cancer screening study using X-ray chest radiographs and sputum cytology, more lung cancers were detected in the screening group compared to the control group, and their survival improved, but there was no reduction in lung cancer mortality. In 2006, the New England Journal of Medicine reported the results of a study of low-dose spiral CT screening by the International Early Lung Cancer Cooperative Study Group. In that study, the 10-year survival rate for clinical stage I lung cancer was as high as 88%, while the 10-year survival rate for surgically treated stage I cases was 92%. The authors concluded that participation in screening reduced the risk of lung cancer death and hypothesized that low-dose spiral CT screening could reduce lung cancer deaths by 80 percent. However, the results of the study by Bach et al. showed that although low-dose spiral CT increased the detection of early-stage lung cancer, it did not reduce the incidence of advanced lung cancer and death, so the current data do not prove that low-dose spiral CT screening reduces mortality from lung cancer. From the perspective of evidence-based medicine, randomized controlled trials are the strongest method to evaluate the effectiveness of lung cancer screening, but most of the current low-dose spiral CT lung cancer screening studies have not established prospective control groups, so prospective randomized controlled studies are needed to prove whether it can reduce lung cancer mortality. Although more early-stage cases are detected in low-dose spiral CT lung cancer screening studies, the false-positive rate is also very high, which means that misdiagnosis is very serious and the risks are manifold. Those who screen positive have to undergo further tests, which can cause serious complications in addition to increased costs and, more seriously, some invasive tests such as biopsy or even chest exploration surgery.