BACKGROUND Pulmonary arterial hypertension (PAH) in patients with congenital heart disease (CHD) usually has a homogeneous pressure distribution. More rarely, complex CHD patients have segmental PAH. This is often post-surgically. The characteristics of these patients and their responsiveness to specific pulmonary vasodilator therapy have not been described. METHODS Seven adults with segmental PAH complicating CHD were treated at 3 specialized adult CHD centers between January 2006 and December 2010. Clinical characteristics, six minute walking distances (6 MWD), laboratory tests and images were obtained from medical records and the responses to Bosentan, an endothelin-1 receptor antagonist, were assessed. RESULTS All patients (mean age 32 (23-42) years, five females) had a primary diagnosis pulmonary atresia (PA), four with major aortopulmonary collateral arteries (MAPCAs). Four segmental PAH patients had a right pulmonary artery stenosis, two a left pulmonary artery stenosis and one a unilateral MAPCA stenosis. All patients were symptomatic (functional class II or III) and bosentan was started empirically. Bosentan treatment led to a significant improvement in functional class compared to baseline (1.7 ± 0.5 versus 2.4 ± 0.5; p<0.01). Mean 6 MWD (available in 6 patients) increased by 62 m (22-150 m) from 386 ± 135 to 448 ± 133 m (p=0.03) after 12 months treatment. Most improvement was seen in patients with low baseline 6 MWD. Higher baseline exercise heart rate was significantly associated with lesser improvement in 6 MWD (r=-0.91 p=0.01). Laboratory results did not change after initiation of bosentan treatment. CONCLUSIONS This small retrospective case series suggested a significant improvement of functional class and exercise capacity after bosentan treatment in patients with segmental PAH. These findings warrant a prospective study of the potential benefit of selective pulmonary vasodilator therapy in these complex patients. Therefore, we call on treating physicians to share similar cases.