Background: Two-dimensional (2D) speckle tracking echocardiography (STE) is anew ultrasound technique allowing the assessment of global and segmental myocardial strain and strain rate. We assessed the feasibility and reproducibility of this technique within a paediatric population. We quantified the correlation between global strains and MRI computed ejection fraction.Methods and Results: 40 post-operative tetralogy of Fallot adolescents wereprospectively included. All patients underwent 2D STE and a cardiac MRI. Globalcircumferential (GCS) and longitudinal (GLS) strains of both ventricles weremeasured using STE modality. We established a new Functional three-dimensional Index (FI) combining GCS and GLS. Ejection fractions were measured by MRI andcompared to FI. Feasibility of STE and MRI analysis in our population were similar(range= 83-88%). GLS and GLS’ rates for the left ventricle were respectively18.5%+/-5.4 and 1.02s-1+/-0.4 as compared with 20%+/-5 and 0.97s-1+/-0.32 for theright ventricle. Strain intra and interobserver variations were low (range=1.4-2.7%).Strain rates had a low reproducibility (range=0.22-0.25s-1). FI and ejection fractionwere well correlated for the left (r=0.61,p=0.001,see=4.0,n=30) and right(r=0.51,p=0.03,see=4.8,n=19) ventricles.Conclusions: STE is a new echocardiographic technique allowing a reproduciblemyocardial function assessment. A simple combination of strains obtained in several dimensions allows a correct left and right ventricular function assessment well correlated to MRI ejection fraction in the specific clinical setting of our study.