The development of low-dose helical computed-tomography (CT) scanning to detect nodules as small as a few mm has sparked renewed interest in lung cancer (LC) screening. The objective of this study was to assess the potential health effects and cost-effectiveness of a one-time low-dose helical CT scan to screen for LC. We created a decision analysis model using baseline results from the Early Lung Cancer Action Project (ELCAP); Surveillance, Epidemiology and End Results (SEER) registry public-use database; screening program costs estimated from 1999 Medicare reimbursement rates; and annual costs of managing cancer and non-cancer patients from Riley et al. (1995) [Med Care 1995;33(8):828-841] and Taplin et al. (1995) [J Natl Cancer Inst 1995;87(6):417-26]. The main outcome measures included years of life, cost estimates of baseline diagnostic screening and follow up, and cost-effectiveness of screening. We found that in a very high-risk cohort (LC prevalence of 2.7%) of patients between 60 and 74 years of age, a one-time screen appears to be cost-effective at $5940 per life year saved. In a lower risk general population of smokers (LC prevalence of 0.7%), a one-time screen appears to be cost-effective at $23100 per life year. Even when a lead-time bias of 1 year is incorporated into the model for a low risk population, the cost-effectiveness is estimated at $58183 per life year. Based on the assumptions embedded in this model, one-time screening of elderly high-risk patients for LC appears to be cost-effective.