The association between large, left-sided patent ductus arteriosus and severe, peripheral, right pulmonary artery stenosis with no other cardiac malformation is an unreported condition that might be misdiagnosed as pulmonary hypertension due to long-standing ductal shunt. A 57-year-old man with supposed hypertensive patent ductus arteriosus underwent confirmatory cardiac catheterization. At angiography, a severe pre-hilar right pulmonary artery stenosis (peak pressure gradient, 65 mmHg) was found to complicate the hemodynamic picture of a moderate-to-large patent ductus arteriosus (QP/QS, 1.7:1), by causing pulmonary hypertension (mean pressure, 65 mmHg) and left-to-right pulmonary flow imbalance. Both lesions were treated in a single procedure of right pulmonary artery stenting and patent ductus arteriosus closure, after which the pulmonary artery pressure significantly decreased (mean, 35 mmHg). In our opinion, a thorough hemodynamic evaluation followed by pulmonary angiography should be mandatory before proceeding to patent ductus arteriosus closure in the adult patient who has "hypertensive" ductus, in whom possible associated malformations can be missed due to a poor echocardiographic window.