Lung cancer is the leading cause of cancer death in Brazil. While low-dose computed tomography (LDCT) screening is effective for early detection, its implementation in the Unified Health System (SUS) faces significant barriers. This study, based on interviews with 18 specialists, mapped these barriers using the Consolidated Framework for Implementation Research (CFIR). The results reveal multifaceted challenges. Within the innovation characteristics domain, there is uncertainty about applying international evidence to the Brazilian epidemiological context, with a risk of increased false positives due to diseases like tuberculosis. The outer setting points to regional inequalities and unstable funding as major obstacles. In the inner setting, the scarcity of human resources and equipment, and the lack of care coordination were highlighted. Individual barriers include a shortage of specialized professionals, the need for training, and low patient adherence, influenced by logistical factors and the stigma of the disease. Finally, the implementation process is hindered by the absence of robust data for effective planning and continuous monitoring. The study concludes that for successful implementation, it is essential to consider and plan solutions for these barriers, adapting the policy to the complex reality of the SUS.