Background: The American Cancer Society (ACS) partnered with two federally qualified health centers (FQHCs) and American College of Radiology designated lung cancer screening facilities on a two-year pilot project to implement lung cancer screening. The project aimed to develop a referral program and care coordination practices to move patients through the screening continuum and identify critical facilitators and barriers to implementation. Methods: Evaluators conducted key informant interviews (N=46) with navigators, clinical staff, administrators from both sites, and ACS staff during annual site visits in 2017 and 2018 to capture data on implementation barriers and facilitators. Three evaluators conducted a thematic analysis using the Consolidated Framework for Implementation Research (CFIR) and assessed factors associated with effective implementation and improved screening outcomes.Results: One study site established a sustainable lung screening program, while the other encountered numerous implementation barriers which they failed to overcome. CFIR constructs highlighted critical barriers and factors associated with success and improved outcomes. Intervention Characteristics: Time spent with patients and disruption to normal workflows were challenges to implementation at both sites. Outer Setting: Both sites struggled with building patient trust and worked to gain trust by providing clear, consistent information about the screening process. One site was located in a state with Medicaid expansion that reimbursed screening but the other was not. Inner Setting: Engaged, supportive leaders who provided clear, consistent communication about implementation helped improve staff capacity, which was critical to building a successful program. Individual Characteristics: Knowledgeable, confident champions and intervention leaders were able to train, guide, and motivate staff throughout the intervention, whereas the absence of supportive leadership failed to produce staff champions and intervention leaders. Process: A slow, stepwise approach to implementation at one site allowed project champions to pilot-test the referral and reimbursement processes and resolve issues before scaling-up.Discussion: This pilot project provides insight into critical resources and steps for successful program implementation in underserved FQHC settings. Future efforts could build upon these findings by considering self-assessment and monitoring tools that incorporate CFIR constructs to help identify and address possible facilitators and barriers to implementation of LDCT.