The treatment of pulmonary arterial hypertension (PAH) has undergone significant change in recent years, improving both quality of life and survival for patients. One of the principal new agents is sildenafil, a phosphodiesterase-V inhibitor with great PAH efficacy. Its success has led to consideration of other phosphodiesterase inhibitors not yet licensed for pediatric PAH including tadalafil and vardenafil, among others. This article summarizes the evidence base for phosphodiesterase inhibitors used to ameliorate pediatric PAH pathology and associated symptoms. It also analyzes their suitability for contemporary practice with the aim of clarifying and helping to direct regimens that produce improved patient outcomes.