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Evaluating diastolic function in children remains a topic of clinical discussion and a gold standard measurement technique is still lacking. Wave intensity analysis can provide insight into ventricular filling mechanisms and ventriculo-vascular coupling, and it can be derived directly from cardiovascular magnetic resonance (CMR) imaging data, specifically from routine phase-contrast flow acquisitions, by defining wave intensity in terms of simultaneous changes of velocity and fractional changes of area. This method was applied to a group of 53 cases (12 healthy controls, 12 congenital aortic stenosis, 11 hypertrophic cardiomyopathy, 8 restrictive cardiomyopathy, 10 dilated cardiomyopathy). All patients also had full CMR and echocardiographic examinations. A new wave intensity parameter FCW/FEW was defined (=ratio of peak forward compression wave in early systole, typically associated with ventricular dP/dt, and peak forward expansion wave at end systole, associated with diastolic time constant τ) and compared with accepted indicators of diastolic dysfunction, i.e. left atrium area from CMR, E/A ratio, E/E’ ratio and E-wave deceleration time (DT) from echo. Differences between cohorts were firstly appreciated in terms of ejection fraction and aortic distensibility. Receiver operating characteristic (ROC) curves then revealed that FCW/FEW, LA area and E/E’ ratio were overall good, statistically significant discriminators between controls and patients with presumed compromised diastolic function, while E/A and DT failed to differentiate (Fig. 1, Table 1). This study proposes CMR-derived wave intensity analysis as an additional medium to non-invasively investigate diastolic function in children, contributing to a point of on-going clinical debate. Parameter AUC p Value FCW/FEW 0.881 <0.001* LA area 0.846 0.001* E/A 0.412 0.398 E/E’ 0.884 <0.001* Dec time 0.380 0.247 Table 1(AUC = area under the curve)