Non-invasive ventilation (NIV) has been shown to improve survival and quality of life in COPD patients with chronic hypercapnic respiratory failure. However, the proportion of COPD patients with chronic hypercapnia is not yet known and clinical data enabling better identification of patients are scarce. The HOmeVent registry was initiated to determine the prevalence of chronic hypercapnia in COPD in an outpatient setting and to evaluate the predictors of hypercapnia. HOmeVent is a multicenter, prospective, observational, non-interventional patient registry that includes COPD patients in GOLD stage 3 or 4. Eligible patients were identified and enrolled in an outpatient setting during routine clinic visits. Assessments included blood gas analyses, pulmonary function testing and quality of life assessment. Ten outpatient clinics in Germany enrolled 231 COPD patients in the registry (135 in GOLD stage 3 (58%) and 96 in GOLD stage 4 (42%)). Arterial carbon dioxide pressure (PaCO ) was ≥45 mmHg in 58 patients (25%); of these, 20 (9%) had PaCO ≥50 mmHg. The prevalence of hypercapnia at both cut-off values was numerically higher for patients in GOLD stage 4 versus 3. An increased body mass index, a decreased forced vital capacity and an increased bicarbonate level were significant independent predictors of hypercapnia. The proportion of patients who received NIV was 6% overall and 22% of those with hypercapnia. A relevant proportion of COPD patients in GOLD stage 3 and 4 exhibits chronic hypercapnia and might, therefore, be candidates for long-term domiciliary NIV treatment.