Background: Deteriorating ventricular function is a major concern after Senning operation. Echocardiographic assessment of right ventricular (RV) function is limited because of the complex geometry of this ventricle. A myocardial performance index (MPI) that is a Doppler‐derived nongeometric measurement has been reported in adults and children. Because this index is independent of geometry it may be particularly useful in the evaluation of the RV function. The aims of this study were: (1)‐ to prospectively determine normal values for RVMPI in patients in the late follow‐up of Senning procedure; (2)‐ to correlate the ejection fraction (EF) and dP/dt measured by echocardiography (ECHO) with the EF measured by magnetic resonance imaging (MRI). Methods: From August 1999 to March 2003, 44 patients submitted to Senning procedure were prospectively studied by echo and MRI. Mean age was 16.7 years (12–26 years). Mean postoperative period was 15.3 years (10–23.5 years). Forty‐one patients were in NYHA Class I, and 3. The RVMPI was calculated using PW Doppler from tricuspid inflow and aortic outflow, the EF by the modified Simpson's rule, and the dP/dt by CW Doppler tricuspid regurgitation signal. All patients underwent MRI and Echo within one month. The Echo results were compared to RV EF calculated by MRI. Results: RVMPI ranged from 0.16 to 1.42 (mean = 0.50). The EF calculated by echo ranged from 6% to 63% (mean = 39%). Th dP/dt was calculated in 29 raging from 457 to 3213 mmHg/s (mean = 1398 mmHg/s). By MRI the EF ranged from 16% to 85% (mean = 60%). A cut‐off value of 0.47 for the RVMPI was determined (ROC curve), with a sensitivity of 75% and a specificity of 62.5%. There was no correlation between the EF and dP/dt calculated by ECHO and the EF calculated by MRI (R2= 0.29 and 0.04 respectively). The NYHA functional classes of the patients did not correlate with RVMPI or MRI values (Kappa). Conclusion: (1)‐Patients with normal RV function had RVMPI values <0.47, and this index could be useful in the evaluation of Senning procedure; (2)‐ no correlation between the EF and dP/dt calculated by ECHO and the EF calculated by MRI was found.