Background: Left ventricular noncompaction cardiomyopathy (LVNC) is associated with poor clinical outcome in childhood. Standard diagnostic criteria are still controversial, especially in young patients. Recent studies in adults demonstrated that left ventricular (LV) twist is abnormal in LVNC, but it has not been investigated in pediatric patients to date. Our aim was to assess LV cardiac mechanics, LV twist, and the prevalence of rigid body rotation, using 2-dimensional speckle tracking echocardiography, in young patients with LVNC and LV hypertrabeculation. Methods: Forty-seven children (age range: 0–18 years) were assessed for suspected LVNC. All patients underwent 2-dimensional speckle tracking echocardiography and cardiovascular magnetic resonance imaging at 1.5 Tesla (T). Twenty-three patients fulfilled the cardiovascular magnetic resonance imaging diagnostic criteria for LVNC (LVNC group), while the remaining 24 did not and were included in the LV hypertrabeculation group. Forty-seven age- and sex-matched healthy volunteers were used as controls. Results: The average LV twist was significantly reduced in LVNC compared with control and LV hypertrabeculation. Rigid body rotation was recognized in 13 (56%) children with LVNC and in 1 (4%) child with LV hypertrabeculation and a strong family history for LVNC. Multivariable analysis demonstrated that LV twist is an independent predictor of LVNC ( P =0.006; coefficient=0.462). The receiver operating characteristics curve showed that LV twist had optimal predictive value to discriminate patients with LVNC (cutoff value <5.8°; sensitivity, 82%; specificity, 92%; area under the curve=0.914). Conclusions: LV twist has good predictive value in diagnosing LVNC in young patients. Our findings strongly support the routine use of 2-dimensional speckle tracking echocardiography in the evaluation of young patients with suspected LVNC.