Lung cancer (LC) is the most common cancer worldwide. The prevalence of LC and rate of associated mortality are high and increasing faster in China than in Western countries. Non-small cell lung cancer (NSCLC) accounts for most LCs. This study aims to be the first large, multi-center, non-interventional retrospective study of treatment patterns (type/duration, number of lines, completion rate), real-world outcomes, and medical costs among Chinese patients with advanced/metastatic NSCLC (IIIb/IV) or extensive-stage small cell LC (ES-SCLC). This study will enroll 8,800 patients (≥18 years, with a diagnosis of advanced/metastatic NSCLC made between 1 December 2013 to 30 November 2014) from 35 to 50 Chinese sites. Hospital information systems (HIS) and electronic medical records will be retrospectively reviewed, in adherence with regulatory and ethical requirements. Early-stage treatment (starting from 1 December 2010) of patients with recurrent disease or early disease progression will be examined. Data will be collected at baseline (diagnosis) and 6 and 12 months after this. Observation will end after 3 years or death. Data will be stratified by histology, staging, age, region, health insurance, and epidermal growth factor receptor (EGFR)/anaplastic lymphoma kinase (ALK) mutation status. Treatment duration and overall survival will be estimated using Kaplan-Meier curves. Descriptive statistics will be used for disease characteristics and patient demographics. Cox-proportional hazards models will be used to examine the impact of demographics/treatment on survival. Treatment patterns and outcome predictors will be explored using multivariate logistic regression. This protocol describes the methodology for collecting real-world data to guide evidence-based clinical practice and inform unmet needs in NSCLC treatment, with potential to identify gaps between guidelines and current practice. NCT03505515; data registered on ClinicalTrials.gov: 12h Apr., 2018. 2020 Translational Lung Cancer Research. All rights reserved.