The ethmoidal sinuses are a group of small air-filled spaces located within the ethmoid bone, situated between the eyes and behind the nose. They are part of the paranasal sinuses, which help to lighten the skull, produce mucus, and improve voice resonance. The ethmoidal sinuses are divided into anterior and posterior groups, each draining into the nasal cavity. These sinuses can become inflamed or infected, leading to a condition known as ethmoiditis. Symptoms may include nasal congestion, facial pain, and headaches. Proper drainage of the ethmoidal sinuses is essential for maintaining sinus health and preventing complications.