Frontal sinus drain into:
The frontonasal duct is a communication between the frontal air sinuses and their corresponding nasal cavity. The duct is lined by mucous membrane. The duct empties into the nasal cavity middle nasal meatus through the infundibulum of the semilunar hiatus. Ref: Dhingra 6th edition pg 136.
superior meatus
Inferior meatus
Middle meatus
Ethmoid recess
Nose and paranasal sinuses