The term sinobronchial syndrome is often used, but there is no generally accepted definition. Due to the functional and clinical unity of the whole respiratory tract infectious and allergic irritations lead to homogeneous reactions of the bronchi and the paranasal sinuses. On the other hand there are hints that a disease in one region can cause problems in the other or reinforce it. Probably bronchi and sinuses can also become infected simultaneously from the pharynx. In chronic cases sinusitis and bronchitis are often only symptoms masking an underlying disease that requires differentiated diagnostics and treatment, e.g. cystic fibrosis, primary ciliary dyskinesia, and immunological defects.