BACKGROUND: Lung cancer has the highest mortality-rate per cancer, with an overall 5-year survival <15%. Several non-randomized studies pointed out the high sensitivity of low dose computed tomography (LDCT) to detect early stage lung cancer. In France, Depiscan, a pilot RCT of LDCT versus chest X-ray (CXR), started on October 2002 to determine the feasibility of enrollment by general practitioners (GPs), investigations and diagnostic procedures by university hospital radiologists and multidisciplinary teams, data management by centralized clinical research assistants, and anticipate the future management of a large national trial. METHODS: GPs and occupational physicians (OPs) selected and enrolled 1000 subjects in 1 year. Eligible subjects were asymptomatic males or females aged 50-75 years with a current or former cigarette smoking history of >/=15 cigarettes per day for at least 20 years (former smokers having quit <15 years prior to enrollment). Based to randomization, annual LDCT or CXR screenings were planned at baseline and annually for 2 years. RESULTS: Between October 2002 and December 2004, 765 subjects were enrolled by 89 out of the 232 participating GPs and OPs. Complete clinical and imaging baseline data were available for 621 individuals out of the 765 enrolled, due to 144 noncompliant subjects who withdrew their consent. At least one nodule was detected in 152 out of 336 subjects (45.2%) in the LDCT screening, versus 21 out of 285 subjects (7.4%) in the CXR screening arm. Eight lung cancers were detected in the LDCT arm and one in the CXR arm. DISCUSSION: This pilot trial allows estimating that non-calcified nodules are 10 [6.36-17.07] times more often detected from LDCT than from CXR. However enrollment by GPs was more difficult than expected with 41% active investigators and a high rate (19%) of noncompliant patients. This experience speaks to the need for a high level of GPs formation and a large, coordinated clinical research team in such a trial. Trial registration number: 02526.