This study assessed the use of positron emission tomography (PET) in identifying and diagnosing solitary pulmonary nodules (SPNs). For this a decision analysis model was constructed, and three alternatives were compared: wait and watch (WW), PET and anatomical computed tomography (PET), and CT plus PET (CT+PET). Transition probabilities were estimated from published data and consultations with experts. Costs of diagnosis were derived from the French reimbursement scale, and treatment costs from a national hospital database of diagnosis-related groups. The base case was defined as a 65-year-old male smoker with a 2-cm SPN and an associated high risk of malignancy of 43%. Evaluation criteria included incremental cost-effectiveness ratios and the proportion of unnecessary operations avoided in patients without malignant SPN. For the base case WW was the least effective and cheapest strategy. CT+PET was more effective and presented lower incremental cost-effectiveness ratio (<euro>3,022 per life-year gained). It also was superior to PET in cost-effectiveness terms and resulted in 4.3% fewer unnecessary resections of benign SPN than did PET. Risk profile analyses performed on SPN malignancy risk showed that CT + PET remains the most cost-effective strategy in the range of 5.7-87%, and that WW is more cost-effective in the range of 0.3-5.0%. CT+PET is thus cost-effective in detecting malignant SPN in patients with a risk of malignity of at least 5.7% and may avoid inappropriate resections of benign SPN. These findings support the attempts to introduce a larger number of PETs in France for SPN diagnosis.