Inclusion Criteria:  Male and female subjects aged 55-79 years Current or former smokers Subjects with calculated risk score PLCOM2012 ≥1.58% (6 yrs.) or NELSON inclusion criteria (current or former smokers [those who had quit ≤10 years ago] who had smoked >15 cigarettes a day for >25 years or >10 cigarettes a day for >30 years). Able and willing to give written informed consent In addition, non-qualifying subjects fulfilling inclusion criteria 1 (age), 2 (smoking history) and 4 (consent), but do not meet the inclusion criterion 3 (risk too low) will be asked to volunteer by contributing long-term outcome data informing of the development of lung cancer or death from lung cancer (about n=7100 randomly selected from all 3 centers, low-risk group). These subjects will be contacted via mail after a minimum of 5 year follow up to inquire if they developed lung cancer in the time between their recruitment and present. Non-responders will be followed by local registries and by phone. New lung cancer cases will be verified using official hospital or cancer registry documents.  Exclusion Criteria:  Comorbidity, which would unequivocally contraindicate either screening or treatment if lung cancer is detected. History of chest CT within the past year preceding the invitation. Inability to undergo non-contrast CT (e.g. ≥ 200 kg body weight, inability to lie flat). Pregnancy  Risk of non-compliance with study procedures.  Unable to give written consent Patient's inability to fill in the questionnaire self-dependent Limited knowledge of the German language Inability to travel, residents of care facilities, etc.