The role and utility of equilibrium radionuclide angiocardiography was estimated in non-invasive diagnosis of patients with Chronic Obstructive Pulmonary Disease (COPD). In 26 healthy subjects the average value of Right Ventricular Ejection Fraction (RVEF) was 54.8 +/- 7.2, versus 40.89 +/- 7.85 in 37 patients with COPD. Right heart catheterization was performed on 9 patients with COPD, randomly chosen, to analyze the correlation between RVEF values and average Pulmonary Artery Pressure (PAP) values: the correlation index was significantly high (r = 0.80). Moreover, an important agreement was observed between RVEF and PaCO2 values (r = 0.77).