OBJECTIVES: Based on evidence from the National Lung Cancer Screening Trial (NLST), the U.S. Preventive Services Task Force(USPSTF) recently recommended annual low-dose computed tomography(LDCT) screening for patients that are age 55-80, have a 30 pack-year smoking history, and currently smoke or quit within the past 15 years. Under the terms of the Affordable Care Act, participating plans must cover this screening procedure. We project the 5-year clinical, resource, and budget impact of implementing this policy. METHODS: We developed a forecasting model to estimate the 5-year incremental outcomes of implementing LDCT screening in accordance with USPSTF recommendations versus no screening.  We considered commercial (age <65) and Medicare (age 65+) populations with 165.1 million and 51.7 million enrollees, respectively (in accordance with national insurance estimates). Age-specific lung cancer detection rates and stage at diagnosis was derived from the NLST. Included costs were LDCT screening and follow-up, confirmatory bronchoscopy/biopsy, and stage-specific treatment (initial,continuing,terminal care). We estimated lung cancers detected, LDCT scans, and the total and per-member per-month(PMPM) budget impact of covering LDCT screening, assuming 100% adherence to USPSTF recommendations in the base case. Monetary results are reported in 2013 USD and discounted at 3% per year. RESULTS: In commercial and Medicare plans, LDCT screening is expected to result in 84,000 and 141,000 more lung cancers detected (predominantly Stage I),22.4 million and 37.5 million more LDCT scans,and increased overall expenditure of $16.4 billion(PMPM=$1.65) and $27.4 billion(PMPM=$8.84), respectively. The most influential parameters were the proportion of “high risk” patients electing to undergo screening, the rate of screening adoption in the community, and the initial treatment cost of early-stage lung cancer.  CONCLUSIONS: Our analysis suggests that coverage of LDCT lung cancer screening is expected to increase lung cancer diagnoses,result in a greater proportion of early-stage disease diagnoses, and substantially increase health plan expenditure, particularly in Medicare.