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INTRODUCTION The relationship between chronic obstructive pulmonary disease (COPD) and the overall incidence of cancer is poorly understood. The aim of this study was to analyse the incidence of cancer (pulmonary or extrapulmonary) in patients with COPD during follow-up in a specialised outpatient unit, as well as to assess its relationship with the degree of airflow obstruction. METHODOLOGY A prospective observational study was conducted with a cohort of 308 patients with COPD in pulmonology outpatient follow-up consultations from January 2012 to December 2015. The diagnosed malignancies during this period were divided into pulmonary and extrapulmonary. RESULTS The overall incidence rate of cancer, lung cancer and extrapulmonary cancer were 10.3, 3.4 and 7.3 cases per 1,000 patients with COPD per year, respectively. The most common cancers were lung cancer (31%), genitourinary tract cancer (29%) and gastrointestinal cancer (21%). Mild-moderate stages (gradeI-II of the 2009 GOLD classification) and the increase in the pack-year index (PYI) were related to an increase in the onset of malignancies, with an odds ratio (OR) of 2.16 (95% confidence interval [95% CI]: 1.087-4.309; P=.026) and 1.01 (95% CI: 1.002-1.031; P=.023), respectively. CONCLUSION The incidence of extrapulmonary cancer in patients with COPD was twice that of lung cancer; stagesI-II of the 2009 GOLD classification and the PYI were significantly related to the onset of malignancies.