© Author(s) (or their employer(s)) 2018. background Missed injury of the diaphragm may result in hernia formation, enteric strangulation, and death. Compounding the problem, diaphragmatic injuries are rare and difficult to diagnose with standard imaging. As such, for patients with high suspicion of injury, operative exploration remains the gold standard for diagnosis. As no current data currently exist, we sought to perform a pragmatic evaluation of the diagnostic ability of 256-slice multidetector CT scanners for diagnosing diaphragmatic injuries after trauma. Methods A retrospective review of trauma patients from 2011 to 2018 was performed at an American College of Surgeons-verified level 1 trauma center to identify the diagnostic accuracy of CT scan for acute diaphragm injury. All patients undergoing abdominal operation were eligible for inclusion. Two separate levels of CT scan technology, 64-slice and 256-slice, were used during this time period. The prospective imaging reports were reviewed for the diagnosis of diaphragm injury and the results confirmed with the operative record. Injuries were graded using operative description per the American Association for the Surgery of Trauma guidelines. results One thousand and sixty-eight patients underwent operation after preoperative CT scan. Acute diaphragm injury was identified intraoperatively in 14.7%. Most with diaphragmatic injury underwent 64-slice CT (134 of 157, 85.4%). Comparing patients receiving 64-slice or 256-slice CT scan, there was no difference in the side of injury (left side 57.5% vs. 69.6%, p=0.43) or median injury grade (3 (3, 3) vs. 3 (2, 3), p=0.65). Overall sensitivity, specificity, and diagnostic accuracy of the 256-slice CT were similar to the 64-slice CT (56.5% vs. 45.5%, 93.7% vs. 98.1%, and 89.0% vs. 90.2%). Discussion The new 256-slice multidetector CT scanner fails to sufficiently improve diagnostic accuracy over the previous technology. Patients with suspicion of diaphragm injury should undergo operative intervention. Level of evidence I, diagnostic test or criteria.