Right-sided heart failure is a major problem among patients with congenital heart diseases, due to the prevalence of congenital heart defects and the association of pulmonary hypertension. More attention is focused on the structure of the right heart particularly in association with congenital heart defects and chronic lung disease. The right ventricle (RV) may support the pulmonary circulation, and sometimes the systemic circulation (systemic RV) in congenital heart defects. Despite major progress being made, assessing the RV remains challenging, often requiring a multi-imaging approach and expertise (echocardiography, magnetic resonance imaging, nuclear and cineangiography). Evidence is accumulating that RV dysfunction develops in many of these patients and leads to considerable morbidity and mortality. While there is extensive literature on the pathophysiology and treatment of left heart failure, the data for right-sided heart failure is scarce. Therefore RV function in certain groups of congenital heart disease patients needs close surveillance and timely and appropriate intervention to optimise outcomes. An understanding of RV physiology and hemodynamics will lead to a better understanding of current and future treatment strategies for right heart failure. This will review rightsided heart failure with the implications of volume and pressure loading of the RV in congenital heart diseases.