IntroductionLung cancer mortality is increasing in women. In Spain, estimates suggest that lung cancer mortality may soon surpass breast cancer mortality, the main cause of cancer mortality among women. The aim of this study was to estimate the proportion of women at high risk of developing lung cancer in a group of participants in a population-based breast cancer screening program. MethodsCross-sectional study in a sample of women who participated in a population-based breast cancer screening program in 2016 in Hospitalet de Llobregat n = 1,601. High risk of lung cancer was defined according to the inclusion criteria of the National Lung Screening Trial (NLST) and the Dutch-Belgian randomized lung cancer screening trial (NELSON). ResultsAround 20% of smokers according to NLST and 40% of smokers according to NELSON criteria, and around 20% of former smokers according to both criteria, are at high risk of developing lung cancer. A positive and statistically significant trend is observed between the proportion of women at high risk and nicotine dependence measured with the brief Fagerström Test. ConclusionsA high proportion of participants in this breast cancer screening program have a high risk of developing lung cancer and would be eligible to participate in a lung cancer screening program. Population-based breast cancer screening programs may be useful to implement lung cancer primary prevention activities.