Abstract: The invention relates to the combined use of at least one monoterpene which can be applied systemically, in particular perorally, and at least one respiratory tract therapeutic agent which can be applied topically, in particular through inhalation, for the prophylactic and/or therapeutic treatment, in particular combination therapy and/or co-medication, of respiratory tract diseases, in particular bronchopulmonary diseases. Through the combined use of the systemic monoterpene with the topical, in particular inhaled respiratory tract therapeutic agent, the effect or efficiency of the topical or inhaled respiratory disease therapeutic agent can be increased significantly, in particular in a synergistic manner, on the one hand, and the required dosage thereof can be reduced significantly on the other hand, combined with the resulting advantages (e.g., avoidance or reduction of side effects).