Inhaled nitric oxide (NO) is a selective pulmonary vasodilator in patients with end-stage cardiac failure. Preoperative high pulmonary vascular resistance could modify early and late results after heart transplantation generally due to right-ventricular failure. Aim of this study was to assess pulmonary vascular resistance variability following inhalation of NO by using a scintigraphic method. Our preliminary results suggest that inhaled NO in patients with end-stage heart failure redistributes blood away from apical regions and towards more basal and posterior segments, probably dilating blood vessels in ventilated but nonperfused zones. NO may represent a simple and reliable method to evaluate dynamic response of pulmonary vasculature.