Both CMR and MSCT give almost unrestricted access to intra-thoracic structures, whereas ultrasonic access may be limited in ACHD patients. MSCT, generally using intravascular contrast, gives superior spatial resolution more rapidly than CMR, although the radiation dose is a concern in younger patients who may require repeated studies. MSCT gives better visualisation of epicardial coronary arteries and small collateral vessels, and can show conduit calcification or stent location clearly. It provides an alternative to CMR in patients with a pacemaker or ICD. CMR offers unrivalled versatility of acquisition methods without ionizing radiation, enabling measurements of biventricular function, flow, myocardial viability, angiography and more. A dedicated CMR service should be available in a centre specializing in ACHD care. Appropriate understanding is needed for the evaluation of congenitally and surgically altered circulatory function, for example after Fontan operations, surgery for transposition of the great arteries or tetralogy of Fallot.