BACKGROUND Retrospective studies based on clinical data and without spirometric confirmation suggest a poorer prognosis of patients with ischemic heart disease (IHD) and chronic obstructive pulmonary disease (COPD) following percutaneous coronary intervention (PCI). The impact of undiagnosed COPD in these patients is unknown. We aimed to evaluate the prognostic impact of COPD - previously or newly diagnosed - in patients with IHD treated with PCI. METHODS: Patients with IHD confirmed by PCI were consecutively included. After PCI they underwent forced spirometry and evaluation for cardiovascular risk factors. All-cause mortality, new cardiovascular events, and their combined endpoint were analyzed. RESULTS: A total of 133 patients (78%) male, with a mean (SD) age of 63 (10.12) years were included. Of these, 33 (24.8%) met the spirometric criteria for COPD, of whom 81.8% were undiagnosed. IHD patients with COPD were older, had more coronary vessels affected, and a greater history of previous myocardial infarction. Median follow-up was 934 days (interquartile range [25%-75%]: 546-1,160). COPD patients had greater mortality (P=0.008; hazard ratio [HR]: 8.85; 95% confidence interval [CI]: 1.76-44.47) and number of cardiovascular events (P=0.024; HR: 1.87; 95% CI: 1.04-3.33), even those without a previous diagnosis of COPD (P=0.01; HR: 1.78; 95% CI: 1.12-2.83). These differences remained after adjustment for sex, age, number of coronary vessels affected, and previous myocardial infarction (P=0.025; HR: 1.83; 95% CI: 1.08-3.1). CONCLUSION: Prevalence and underdiagnosis of COPD in patients with IHD who undergo PCI are both high. These patients have an independent greater mortality and a higher number of cardiovascular events during follow-up.