ABSTRACT
The paranasal sinuses should be radiolucent on plain radiography in adults; they can be filled with fluid and/or soft tissue in cases of trauma or disease. In children, the paranasal sinuses are much smaller (maxillary and ethmoidal) or even nonexistent (sphenoid and frontal) at birth and progressively pneumatize with age; this is usually complete by the early teen years. The mastoid air cells are normally pneumatized throughout life.
