The ethmoid sinuses are the smallest of the sinuses. They are located between the eye sockets. They are present at birth. By age 12, the ethmoid sinuses reach adult size. They are made up of a honeycomb of 4 - 17 small subchambers known as air cells. These air cells are divided into either anterior or posterior ethmoid air cells. The blood supply from the ethmoid sinuses drains into veins surrounding the eye sockets. Spread of infection from the ethmoid sinuses can infect the tissues around the eyes (periorbital cellulitis). Ethmoid sinus pain often is felt in pain around and behind the eyes.