Previous autopsy studies have found an error rate of nearly 9%, implying that thousands of patients die every year due to diagnostic errors. This systemic review of diagnostic errors in pediatric and neonatal intensive care unit (ICU) settings synthesized results of 13 studies of autopsies that confirmed diagnostic errors. The most common type of missed diagnosis found at autopsy was infection. Other prevalent missed diagnoses included vascular events and congenital conditions. The authors estimate that 6.4% of pediatric ICU deaths and 3.7% of neonatal ICU deaths are attributable to major missed diagnosis. This work argues for more prospective investigation of missed and delayed diagnoses as well as more routine autopsies in pediatric and neonatal ICU settings. A past AHRQ WebM&M commentary discussed the value of autopsies in understanding misdiagnoses.