The paper presents a case of coexistence of the aortic coarctation with TTTS. This rare coincidence and hemodynamic disturbances resulting from hypovolemia interfere with the hemodynamic picture of the structural cardiac defect. Prenatal diagnosis is based on the assessment of the size of both ventricles. If the defect is present, the left ventricle is usually smaller than the right one. Coarctation may be also suspected in case there is disparity between large vessels in the mediastinum. Comparison of the width of the aorta, and ductus arteriosus, especially if the rate is 2:1 in favor of the latter may suggest such defect. Furthermore, the finding of continuous flow through the aortic isthmus increases the likelihood of the defect 16-fold. The presence of "coarctation shelf" in color Doppler may suggest the existence of the cardiac defect that will require an intervention. In the present study the aortic coarctation was diagnosed in the recipient, who presented marked features of hypervolemia in venous Doppler studies, and in echocardiographic assessment of the right heart. The paper presents signs of hemodynamic disturbances in Doppler studies and changes of Doppler blood flow parameters observed during therapy (i.e., amnioreduction, fetoscopy). Diagnosis of coarctation may be hindered by the presence of the right heart volume overload, hypertrophy of the heart muscle as a result of associated hemodynamic disturbances in twin-to-twin transfusion syndrome. The impact of therapeutic interventions such as amnioreduction and fetoscopy the on cardiovascular hemodynamic parameters of both fetuses is also discussed. Also, a wide ductus arteriosus may make it difficult to diagnose this defect in utero. The paper presents diagnostic and therapeutic management in a case of TITS complicated by an aortic coarctation in the recipient.