Right heart catheterisation (reference method) and M-mode echocardiography were performed in 90 patients with chronic respiratory failure (73 BPCO-chronic airflow obstruction and 17 non-BPCO). The aim of this study was to assess the place of echo-cardiography in the diagnosis and assessment of pulmonary arterial hypertension (HTAP) and/or right ventricular hypertrophy (HVD). The results are somewhat deceptive; first as reliable measurements were impossible in 20% of cases (due to airways distension), then because the sensibility of the method is only 75% (only 62.2% in the group with moderate HTAP with a mean pulmonary artery pressure (PAP) between 21 and 30 mmHg, where as the specificity was satisfactory (87.5%). The best coefficient of linear correlation was observed between the PAP and the end-diastolic diameter of the right ventricle (DTDVD) (r = 0.52; p less than 0.001). Such a correlation does not allow for a prediction of an exact level of PAP in individual cases. The combination of 3 non-invasive methods (ECG, Echo-cardiography and myocardial scintigraphy) allows for an excellent overall sensibility (91.7%) but to the detriment of the specificity (66.6% only).