Congenital diaphragmatic eventration (CDE) and congenital diaphragmatic hernia (CDH) with or without hernia sac are three different types of congenital diaphragmatic malformations, which this study evaluates. All surgically treated patients with CDE or Bochdalek type CDH between 2000 and 2016 were included in this retrospective analysis. Demographics, CDH-characteristics, treatment, and clinical outcome were evaluated. In total, 200 patients were included. Patients with an eventration or hernia sac had no significant differences and were compared as patients without a true defect to patients with a true defect. The 1-year survival of patients with a true defect was significantly lower than patients with no true defect (76% versus 97%, p = 0.001). CDH with no true defect had significantly better short-term outcomes than CDH with true defect requiring patch repair. However, at 30 days, they more often required oxygen supplementation (46% versus 26%, p = 0.03) and had a higher recurrence rate (8% versus 0%, p = 0.006) (three eventration and two hernia sac patients). Conclusion: Patients without a true defect seem to have a more similar clinical outcome than CDH patients with a true defect, with a better survival. However, the recurrence rate and duration of oxygen supplementation at 30 days are higher than CDH patients with a true defect.What is Known:• Congenital diaphragmatic hernia with or without hernia sac and congenital diaphragmatic eventration (incomplete muscularization) are often treated similarly.• Patients with hernia sac and eventration are thought to have a relatively good outcome, but exact numbers are not described.What is New:• Congenital diaphragmatic eventration and patients with hernia sac seem to have a more similar clinical outcome than Bochdalek type CDH with a true defect.• Patients without a true defect (eventration or hernia sac) have a high recurrence rate.