The long-term follow-up of patients operated on for congenital diaphragmatic hernia (CDH) at birth has been extensively evaluated, both clinically and with respect to respiratory function. However, little is known about the sports practice and stress performance of these subjects. Fifteen of 107 patients operated on for CDH underwent exercise stress testing with a stepwise increase in workload. A questionnaire was provided, which requested information on sports practice and lifestyle. Maximal oxygen consumption [Vo2 max] was measured along with dynamic lung volumes. Clinical examination included a whole-body assessment (height, weight, skinfolds) and vital parameters (heart rate and blood pressure). Fifteen healthy children who practiced regular physical activity (2 to 4 hours/week) served as controls. All the CDH patients experienced a good lifestyle, but only 8 of them were participating in sports. Exercise duration and Vo2 max were significantly lower for the CDH patients, and were lowest for the sedentary patients. Therefore, the reduced Vo2 max of these otherwise healthy children most likely represents a lower degree of physical fitness rather than decreased respiratory function. Fitness is an expression of well-being; thus, there is evidence that these patients could safely participate in competitive motor activities.