Atelectasis with chronic pneumonitis affecting the right middle lobe secondary to compression of the middle lobe bronchus by enlarged indurated or calcified peribronchial nodes is defined as middle lobe syndrome clinicopathologically. The lesion in this series of case reports including tuberculous lymphadenitis, lung cancer, atelectasis and lung abscess with organizing pneumonitis, had been treated by lobectomy. Postoperative courses were uneventful in all patients. Herewith, we report these four experiences with review of literature.