Objective To compare the chest CT patterns of acute graft-versus-host disease (aGVHD) and infections within 100 days after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in pediatric recipients to help hematologist make definitive diagnosis as early as possible. Methods A total of 143 pediatric recipients from January 2015 to June 2019 who were diagnosed pulmonary aGVHD or infections within 100 days after allo-HSCT were enrolled in this study. Two observers evaluated the extent and distribution (unilateral, bilateral) of the CT patterns. The patterns were then classified as ground-glass opacity (GGO) (localized, patchy, diffuse), consolidation (localized, patchy, diffuse), reticulation (localized, patchy, diffuse), nodules (localized, multiple), bronchiectasis, pleural effusion, air trapping, tree-in-bud sign, and pneumomediastinum. The onset time and radiological patterns of the two cohorts were statistically compared. Results The mean onset time of aGVHD (n = 85) and infections group (viral n = 29, bacterial n = 22, fungal n = 7, total n = 58) was 36.89 +/- 24.34 (range, 10-99 days) and 23.48 +/- 20.65 days (range, 4-94 days) with a significant difference (P = .001). The top three underlying diseases were acute lymphoblastic leukemia (ALL) (n = 49, 57.6%); acute myeloid leukemia (AML) (n = 24, 28.2%); and aplastic anemia (AA) (7.1%) in aGVHD group and hemophagocytic syndrome (HPS) (n = 33, 56.9%); AA (n = 9, 15.5%); and ALL (n = 6, 10.3) in infection group. GGO (41.2%) in aGVHD prevailed on CT, whereas GGO (53.4%) and consolidations (43.1%) were more prevalent in infections. The distribution of GGO showed more diffuse in aGVHD (P = .031) and symmetric while patchier GGO prefers infections (P < .001). No differences were found in the reticulation. Nodules were more common in infections (P = .004) while pleural effusion was more common in aGVHD group (P < .035). Conclusion Imaging patterns of aGVHD on CT differ substantially from that of infections. Physicians and radiologists should be aware of such radiological differences in order to give accurate treatment. Notably, definite diagnosis should be made in combination with clinical manifestations, signs, and laboratory tests.