Inhalation of drugs for pulmonary arterial hypertension is a fascinating concept, combining powerful pharmacologic effects of targeted drugs with pulmonary and intrapulmonary selectivity. Such effects are possible because the lung anatomy allows for application of drugs to the small pulmonary arteries by diffusion from alveolar surfaces. All drugs that have been shown to be efficacious in PAH are strong vasodilators, however, they differ very much concerning their vasodilative mechanisms and concerning their physicochemical properties. Prostanoids are particularly strong vasodilators with anti-remodelling properties but their conventional application has two drawbacks: i) they are prone to systemic side-effects and ii) their application necessitates a continuous intravenous or subcutaneous infusion. Inhaled prostanoids avoid these drawbacks and have been shown to be efficacious in randomized controlled trials. Inhaled iloprost (Ventavis®) has been approved in Europe, US, Australia and many other countries, inhaled treprostinil (Tyvaso®) has been approved in the US. Despite this success there is further space for improvement, particularly concerning more convenient and reliable delivery systems via inhalation.