Very few studies, particularly from oriental population, reported the progression of lung cancer from asymptomatic to symptomatic phase. The present study aimed to estimate mean sojourn time (MST) of lung cancer, an average duration period in which tumour can be asymptotically detected by chest X-ray (CXR), taking into account gender, smoking and histological type. Based on institutional cancer registry for lung cancer patients with prior non-diagnostic CXR (n=221), data were collected on demographic features, histology type, survival status, history of smoking, and asymptomatic or symptomatic status in light of chief complaint at diagnosis retrieved from medical records. The MST for the natural history of lung cancer underpinning a three-state Markov model was estimated with a Bayesian approach. The estimated MST for lung cancer was 5.51 months (95% credible interval: 4.04-7.12). Small cell lung carcinoma was even statistically significantly shorter MST than non-small cell lung carcinoma (3.01 (3-3.98) months vs. 6.07 (4.44-8.25) months). In parallel with literatures reporting tumour growth rate related to CXR and computed tomography (CT), the shorter mean sojourn time by using CXR estimated in our study strongly suggests that CT screening may be more effective in early detection of lung cancer in population-based screening.