The diagnosis of pulmonary hypertension requires an invasive confirmation of an elevated mean pulmonary artery pressure during a right heart catheterization. The present thesis reviews the invasive hemodynamic approaches to assess the functional state of the pulmonary circulation and its impact on right ventricular function in pulmonary vascular diseases. Pulmonary vascular resistance is better characterized by multi-point pressure/flow measurements. The occlusion analysis of the pulmonary artery pressure decay curve permits to locate the site of increased resistance. Pulmonary vascular resistance permits to assess the steady component of the pulmonary circulation, whereas the pulsatile component can be better appreciated by pulmonary vascular impedance. Determination of ventriculo-arterial coupling permits to assess the impact of an elevated afterload on right ventricular function, which ultimately determines symptoms and prognosis of patients with pulmonary hypertension.