Background: Ketamine is an NMDA-receptor antagonist with analgesic and opioidsparing properties. Although well studied in adults, more robust evidence supporting ketamine's use for pediatric pain management is needed. This retrospective study evaluates ketamine's opioid-sparing effectiveness in pediatric and young adult oncology and hematology patients.Procedure: Continuous ketamine infusions administered for pain management between 2010-2020 were reviewed. Data including demographic characteristics, oncology/hematology and pain diagnoses, concurrent pain medications, and ketamine infusions' dose and duration were collected. Opioid consumption data based on delivery via patient-controlled analgesia were collected 1 day before (D1), all days during (cumulatively named D2), and 1 day after (D3) ketamine infusions and calculated as morphine-equivalent doses (mg/kg/day). Data were reported for the entire study group as well as for distinct oncology and end-of-life categories, and short-term acute pain circumstances which included vaso-occlusive crises in hematology patients. Side effects were reviewed.Results: Significantly lower daily opioid consumption was noted in the oncology group, while decreases were not significant in the end-of-life group and in the overall study population. The acute pain group did not show an opioid reduction associated with the ketamine infusions. A largely tolerable side-effect profile was observed, with no differences among each group's incidence.Conclusions: Ketamine infusions were associated with significantly reduced opioid consumption for oncology patients. The opioid-sparing effects of ketamine may vary according to clinical diagnoses and circumstances of use. Overall, low-dose ketamine infusions present an acceptable safety profile in pediatric and young adult patients; nevertheless, individual risks and benefits should be considered.