Background: The main objective of the study was to assess the strain measures (peak systolic longitudinal strain [LAS] and stiffness index [LASt]) and their relation to insulin resistance in obese children.Methods And Results: Eighty obese children (body mass index was 28.2 ± 3. 1) and 60 age-matched healthy nonobese children were recruited. Conventional, tissue Doppler imaging LAS and LASt were measured for all children using 2D speckle tracking imaging (2DSI). Insulin resistance was assessed for obese children. Mean LAS was lower, and mean LASt was higher in obese children as compared to control group (11.3 + 2.2 vs. 38.2 + 11.6, P < 0.001, and 1.12 ± 0.23 vs. 0.21 ± 0.11, P < 0.001, respectively). LASt was significantly correlated with insulin resistance (P < 0.0001), and a value of >1.0 of LASt was the best cutoff value which can predict insulin resistance in obese children with a sensitivity of 92% and specificity of 86%.Conclusions: LAS and LASt differed significantly in obese and nonobese children, in spite of normal left ventricular systolic and diastolic functions. LAS and LASt were associated with insulin resistance in obese children.