We report concurrent pulmonary arterial dissection and saccular aneurysm resulting from primary pulmonary hypertension in a 26-year-old man. The pulmonary trunk was dissected 9 cm along its entire circumference, 3 cm above the pulmonary valvular cusps. In addition, a saccular aneurysm 3.5 cm in diameter had formed at the right pulmonary hilus. Histopathology revealed marked medical degeneration and fragmentation of the elastic laminae in the former lesion and a true aneurysm with attenuation and fragmentation of elastic laminae in the latter. The peripheral vasculature in the lungs showed evidence of increased pulmonary arterial pressure, including plexiform and angiomatoid lesions. We present this unique case and discuss the pathomorphogenesis of these lesions in conjunction with primary pulmonary hypertension.