e18308 Background: Accountable Care Organizations (ACOs) were established under the Affordable Care Act as a new payment model intended to impose greater responsibility on all stakeholders for cost control and quality improvement. Preventive services are an ideal target to monitor the effectiveness of new health care delivery models. We sought to examine and compare the prevalence of breast cancer screening (BCa-S), and prostate cancer screening (PCa-S) between ACO and traditional Medicare beneficiaries. We hypothesized that the use of BCa-S is higher among beneficiaries attributed to an ACO, whereas the use of PCa-S, a non-recommended test, would be unaffected by ACO assignment. Methods: Using a random 20% sample of Medicare beneficiaries, we assessed BCa-S in women aged < 75, (evidence-based cancer screening), and PCa-S in men < 75 (non-recommended cancer screening) between January 1, 2013 and December 31, 2013 with appropriate exclusion criteria following the review of guideline recommendations. ACO coverage was ascertained from the quarterly assignment in the Shared Savings Program ACO Beneficiary-level file. Propensity-score weighting was performed to balance out patient and sociodemographic covariates. Results: Following propensity-score weighting, our final cohorts of ACO and traditional Medicare beneficiaries included 52,987 and 526,063 women for BCa-S; 86,936 and 814,221 men for PCa-S, respectively. The prevalence of screening in ACO vs. traditional Medicare were 35.0% vs. 25.2% for BCa-S, and 54.6% vs. 41.7% for PCa-S (all p < 0.001) Conclusions: The ACO model appears to have a salutary effect on preventive service utilization. Our findings vis-à-vis PCa-S among ACOs are likely a reflection of improved health care access rather than vetted screening practices. There is hope that such nonrecommended screening will decrease if more ACOs are required to move towards a “two-sided” risk shared savings and loss model.