Silent sinus syndrome is defined as a spontaneous and progressive enophthalmos and hypoglobus with hypoplasia of the maxillary sinus and resorption of the orbital floor. It is caused by atelectasis of the maxillary sinus in the presence of ipsilateral chronic hypoventilation of the sinus. The problem may be idiopathic, but the term is now also used to describe cases that follow operation or trauma. We describe three cases, each with a different aetiology, and discuss the clinical and radiographic evaluation of the condition, theories regarding its pathophysiology, and surgical correction.