BACKGROUND Lung cancer (LC) and chronic obstructive pulmonary disease (COPD) are associated with increased morbidity and mortality. The differential clinical and functional features among LC patients with or without COPD have not been defined. OBJECTIVE The aims of this study were to examine the prevalence and underdiagnosis rate of COPD in LC patients and to compare the clinical and functional features of LC patients with and without COPD. METHODS We designed a multicenter hospital-based study including all LC cases diagnosed from January 2014 to August 2016. We assessed epidemiological, clinical, radiological, functional, and histological variables in all cases. RESULTS We recruited 602 patients with LC, most of them men (77.9%), with a median age of 67 ± 15 years. The COPD prevalence among LC patients was 51.5%, with a underdiagnosis rate of 71.6%. The LC+COPD patients were older and the proportion of men was higher compared with the LC-only patients. The LC+COPD patients had more pack-years, more squamous LC, a lower monoxide transfer coefficient (KCO), and higher Charlson index scores than patients with LC only. The median survival of LC-only patients was 37% longer than that of LC+COPD patients (22 vs. 16 months), but this difference was not statistically significant. CONCLUSIONS Among LC patients, COPD is prevalent and underdiagnosed. Patients with LC+COPD more often have squamous LC, have greater comorbidities, and have a lower KCO. More effort should be made for an early diagnosis of COPD to select patients at higher risk of developing LC.