Background The prosthesis commonly used for the treatment of congenital diaphragmatic hernia (CDH) lacks elasticity to replace the diaphragm's mechanical properties and does not follow the natural growth of the child treated. Objective To determine the appropriate properties required for the prostheses, a CT study on healthy patients was conducted. Methods Two methods of diaphragmatic surface analysis are assessed: the diaphragmatic surface is either estimated using surface 2D estimations (method 1), or calculated using length measures on thoracoabdominal CT scans from children (method 2). Patients are divided into two groups depending on their age: group 1: n = 9; median age: 2.0 months (0.1-9.5); group 2: n = 9; median age: 182.6 months (158.5-235.5). Growth factor between the two groups is calculated and the two methods are statistically compared. Results The ratio group 2/group 1 of the diaphragmatic surfaces was 4.3 ± 0.2 on the left side and 4.0 ± 0.2 on the right side for method 1, and 5.1 ± 0.2 on the left side and 5.1 ± 0.3 on the right side for method 2. The difference in the median values between both methods is statistically significant for both the left and right sides (p = 0.022 and p = 0.002, respectively). Hence, the two methods cannot be used exchangeably. Conclusion The treatment of CDH with large defect remains a challenge because of the high incidence of hernia recurrence probably due to prosthesis defect; thus it is important to estimate the diaphragmatic surface precisely. We aim to develop a prosthesis material that can be commonly used and found a mean diaphragmatic growth factor of approximately 4 to 5 from early childhood to adolescence.