The trial is a randomised trial comparing annual CT screening for lung cancer with no screening in 4104 smokers and former smokers between the age of 50 and 70 years. The goals are: 1) to evaluate if annual CT screening can reduce lung cancer mortality by more than 20 % (in collaboration with the NELSON trial in the Netherlands, 2) to evaluate psychological effects of screening including the effects of false positive diagnoses, and 3) to evaluate possible effects on smoking behaviour. The trial is funded in full by the Danish Ministry of Interior and Health.

The trial is a parallel randomized controlled trial comparing either a yearly low dose CT scan or no screening. It is scheduled to enroll 4000 smokers and former smokers, and the study is scheduled to last 5 years, i.e. an initial (prevalence) screening is followed by 4 annual (incidence) screenings.

In addition the following investigations are done: A prospective, longitudinal questionnaire assessment of enrolled participants who have received a false positive diagnosis. The questionnaire will focus on the consequences of receiving a false positive diagnosis. Answers from enrolled subjects who have received a false positive diagnosis will be compared to their own "baseline" responses, and responses from subjects who have received a negative result of their own low-dose CT scans All participants will annually be questioned regarding smoking habits, their motivation for cessation of smoking and will be advised to refrain from smoking to assess the effect of participation in a screening protocol for lung cancer on cessation of smoking.

Socioeconomic consequences of screening for lung cancer will be assessed by longitudinal registration of costs and benefits (e.g. morbidity, hospitalization, GP consultations etc.

Assess the value of PET scanning when screening for lung cancer.

Inclusion Criteria:

• Smoking exposure > 20 pack years
• Quit smoking < 10 years
• Fit to undergo treatment
• Pulmonary function test > 30 % of expected (FEV1)

Exclusion Criteria:

• Bodyweight > 130 Kg
• Formely treated for lungcancer, breastcancer, melanoma or hypernephroma.
• Serious co-morbidity with life expectancy below 10 years.
• Treated for other malignant diseases within the last 5 years.
• Treatment for pulmonary tuberculosis within the last 2 years.