BACKGROUND: Patients with COPD generally complain of very different degrees of dyspnea regardless of their pulmonary function. The study, we assessed the right ventricular ejection fraction in relation to dyspnea in COPD patient. METHODS: The pulmonary function including the diffusion capacity was measured. The right ventricle ejection fraction (RVEF) was measured using a first-pass radionuclide scan by multigated acquisition (MUGA). Forty patients with chronic obstructive pulmonary disease (COPD) were stratified for dyspnea according to the Medical Research Council (MRC) scale. Moderate dyspnea and severe dyspnea is defined as MRC 2/3 (n = 16) and MRC 4/5 (n = 24) respectively. RESULTS: The baseline pulmonary function tests including DLCO and the resting arterial blood gas were similar in the moderate and severe dyspnea group, with the exception of the residual volume (% predicted) (moderate 160 +/- 27, severe 210 +/- 87, p < 0.03). The right ventricle ejection fraction was significantly (p < 0.001) lower in the severe dyspnea group (25 +/- 8) than in the moderate group (35 +/- 6). The independent factor assessed by multiple logistic regression revealed only the severity of dyspnea to be significantly associated with RVEF (p < 0.02). CONCLUSION: This study showed that the right ventricle ejection fraction would contributes to severity of dyspnea in patients with a similar pulmonary function.