Even though they seldomly occur, the complications of sinusitis may be life-threatening. Complications can be local, orbital, and intracranial problems or combinations thereof. Orbital complications are the most frequent, and children with acute ethmoiditis are especially prone to them. To prevent permanent loss of vision, immediate and intense therapy is most important. Intracranial complications can have few symptoms, and discordance between symptoms and severity is not uncommon, which involves the importance of early radiologic diagnosis with computed tomographic or magnetic resonance imaging scans. Orbital and intracranial complications of sinusitis are medical emergencies and must be treated by specialists. Whenever possible, the underlying sinus infection should be drained at the same time. All physicians treating acute and chronic sinusitis must keep the potentially life-threatening complications of sinusitis in mind and remain suspicious because early recognition and treatment are crucial in these cases.