Upper and lower airways may be considered as a unique entity, interested by coexisting inflammatory processes that share common etiopathogenic mechanisms. Previous studies have strongly demonstrated a relationship between rhinosinusitis and asthma. This has led to the introduction of the concept of United Airways, which has also been included in the WHO document Allergic Rhinitis and its Impact on Asthma (ARIA); this concept has important consequences also on the treatment of these disorders. To better summarize the evident connection between upper and lower airway disease we decided to describe it as a multilayered construction, each level pointing out more deeply the relationship between these entities.