Eventration of the diaphragm is an abnormal elevation of an intact diaphragm. There are two distinct etiologic types of eventration, congenital and acquired. Congenital eventration is characterized by muscular aplasia, and acquired eventration is caused by injury to the phrenic nerve. The one-year-old girl had recurrent respiratory inflammations and permanent cough since she was two months old. Examinations, such as chest radiogram, chest and abdominal ultrasound, liver doppler, computed tomography of thorax and abdomen, did not distinguish eventration from possible tumorous formation in the right lower lung. The eventration of the diaphragm and atelectasis of the right lower lobe was confirmed during the surgery. Diaphragmatic plication was done, and atelectactic lobe as well as hypoplastic part of the diaphragm were removed. The eventration was confirmed pathohystologically.