Background/Aim: This study characterized lung cancer (LC) in Portugal, to capture sex differences, regional variation, and spatial distribution. Patients and Methods: Variables: age, sex, vital status, region of residence, degree of urbanization, histologic types and stage at diagnosis. Spatial analyses conducted to identify high (HIC) and low incidence (LIC) clusters. Results: In total, 11,642 cases were diagnosed (76.6% male, 23.4% female), with a similar mean age at diagnosis. There were 23,6% locally advanced and 58.4% metastatic disease cases, with 13.4% alive five years after diagnosis. Nonsmall-cell LC accounted for 77.3% of which 40.8% was adenocarcinoma and 22.7% was squamous cell carcinoma. Standardized incident rate (IR) was 37.5/10 5 , 65.2/10 5 in males, and 15.7/10 5 in females, with four HIC (urban) clusters and four LIC (non-urban). Conclusion: This study highlighted the sex differences in incidence, mortality, histology, and geographic distribution of LC in Portugal. Considering the advanced stages and the poor overall survival, understanding sex and geographic differences is important for public health interventions. Worldwide, lung cancer (LC) remains the leading cause of cancer incidence and mortality, with 2.1 million new LC cases (11.6% of the total) and 1.8 million deaths reported in 2018, representing 18.4% of all cancer deaths (1). In males, LC is the most frequent cancer and the leading cause of cancer-related death, while amongst females it is the third most frequent and second cause of cancer-related death (1). Incidence rate (IR) and patterns of LC vary according to the geographical area, ethnicity, differences in tobacco exposure (including intensity and duration of smoking), type of cigarettes, and degree of inhalation, as well as, environmental factors (1, 2). Globally, there is a reported higher LC incidence in males than females with a sex ratio of 2.1:1 (2, 3). In 2017, within the European Union, LC had the highest predicted age-standardized cancer mortality rate in both sexes, corresponding to about 20% of total cancer deaths (4). Since 2012, LC mortality in females has risen by 5.1% whereas it has decreased by 10.7% in males. This decrease in male LC mortality correlates with the decreased prevalence of smoking in males in recent decades (4). In Portugal, LC is the fourth most common cancer representing 9.8% of all cases and the main cause of cancer-related mortality (17.3%) in 2018 (5). Regarding sex, LC is the third most frequently occurring cancer in males and the fourth in females with a male to female IR of 3.1:1 (5). According to the last report in 2017, published by Direção Geral da Saúde (DGS)
