Policy1-Lung is an in-development microsimulation model of the natural history of lung cancer. As the vast majority of lung cancer is caused by smoking; Policy1-Lung must model the relationship between individual smoking behaviour and age-specific tumour incidence. The effect of smoking on mortality from causes other than lung cancer must also be included in the simulation. Finally, to facilitate interventions on disease progression and mortality, the stage progression and survival after diagnosis must also feature. Once calibrated, we aim to use Policy1-Lung to model the impact on quality-of-life and life expectancy of interventions such as lung cancer screening, smoking cessation, early diagnosis and management of lung cancer, and new treatments.