AbstractSpace‐time analysis of mortality risk is useful to evaluate the epidemiologic transitions at the subnational level. In our study, we analysed the death certificate records for lung cancer in Italy in 1995‐2016, obtained from the Italian National Institute of Statistics. Our objective was to investigate the spatial‐temporal evolution of lung cancer mortality by sex and province of residence (n = 107) using the birth cohort as relevant time axis. We built Bayesian space‐time models with space‐time interactions. Among males (n = 554 829), mortality peaked in the 1920‐1929 cohort, followed by a generalised decline. Among females (n = 158 619), we found novel original evidence for a peak in the 1955‐1964 cohort, equivalent to a 35‐year delay, with a downward trend being observed thereafter. Over time, the documented north‐south decreasing mortality gradient has been replaced by a west‐east decreasing gradient. Naples has become the province at highest risk in Italy, both among males and females. This pattern is consistent with an epidemiologic transition of risk factors for lung cancer to the south‐west of the country and raises concern, because 5‐year age‐standardised net survival from the disease in this geographic area is lower than in northern and central Italy. The variability of mortality rates among provinces has changed over time, with an increasing homogeneity for males and an opposite trend for females in the more recent birth cohorts. These unprecedented observations provide evidence for a profound spatio‐temporal transition of lung cancer mortality in Italy.