National Taiwan University Hospital Chu-Tung Branch initiated the lung cancer screening by LDCT since June 2015. Many people can get the LDCT screening with affordable price with the subsidy from enterprise donation. The purpose of this study is observing those participants with 2-year follow-up. Furthermore, those data may connect with another study of "Low dose computed tomography screening study in nonsmoker with risk factors for lung cancer in Taiwan" （Non-smoker study）which is implemented in other hospitals in Taiwan.