Pulmonary Hypertension (PH) is definited by a mean pulmonary artery pressure (PAPm) >25 mmHg at rest. The Dana Point 2008 Revised Classification System represents the most recent classification system update with respect of various etiologies of PH. About 10 % of adolescents or adults with uncorrected congenital heart disease (CHD) with left-to-right shunt and high pulmonary blood flow develop Pulmonary Arterial Hypertension (PAH) . Progressive vascular remodeling and increase in pulmonary vascular resistance (PVR) may ultimately lead to reversal of the shunt (pulmonary to systemic) causing cyanosis and determining the so-called Eisenmenger Syndrome (ES). Recent advances in the early diagnosis and medical targeted treatment of adult patients with CHD-PAH and ES can improve PAP, PVR and exercise tolerance, together with NYHA Class and survival, and may potentially reverse the vascular remodeling process in selected patients.