41 patients suffering from Chronic Obstructive Lung Disease (COLD) and 44 with Sarcoidosis were studied. Said patients underwent respiratory function tests, echocardiography (M.mode) to assess the right ventricular index ( RVI = diameter of the right ventricular cavity corrected by body surface) and the thickness of the right ventricular anterior wall ( RVAWT ); patients also underwent right heart haemodynamics (Swan-Ganz catheter). These data were further statistically studied by means of multiple regression in order to assess the eventuality of a non-invasive prediction of pulmonary artery mean pressure (PAP): variables taken into consideration were: age, body surface (BS), RVI , RVAWT , arterial oxygen pressure (PaO2), arterial carbon dioxide pressure (PaCO2) and PAP dependence according to each case group and the interaction of each group itself on the variables. RVI appeared to be the most reliable, in fact, when PaCO2 is also available, the standard error of estimation (SEE) was only 3.84 mmHg and the coefficient of determination was equal to 85.5% with a notable improvement when compared to results seen in previous studies. This behaviour was observed both in patients with early sarcoidosis and in COLD patients with mild pulmonary hypertension. This might be due to the fact that we took the right ventricle into consideration which inevitably feels the increase in pulmonary hypertension.