Background This study aimed to explore the imaging characteristics,diversity and changing trend in CT scans of pediatric patients infected with Delta-variant strain by studying imaging features of children infected with Delta and comparing the results to those of children with original COVID-19.Methods A retrospective,comparative analysis of initial chest CT manifestations between 63 pediatric patients infected with Delta variant in 2021 and 23 pediatric patients with COVID-19 in 2020 was conducted.Corresponding imaging features were analyzed.In addition,the changing trend in imaging features of COVID-19 Delta-variant cases were explored by evaluating the initial and follow-up CT scans.Results Among 63 children with Delta-variant COVID-19 in 2021,34 (53.9％) showed positive chest CT presentation;and their CT score (1.10 ± 1.41) was significantly lower than that in 2020 (2.56 ± 3.5) (P =0.0073).Lesion distribution:lung lesions of Delta cases appear mainly in the lower lungs on both sides.Most children had single lobe involvement (18 cases,52.9％),14 (41.2％) in the right lung alone,and 14 (41.2％) in both lungs.A majority of Delta cases displayed initially ground glass (23 cases,67.6％) and nodular shadows (13 cases,38.2％) in the first CT scan,with few extrapulmonary manifestations.The 34 children with abnormal chest CT for the first time have a total of 92 chest CT examinations.These children showed a statistically significant difference between the 0-3 day group and the 4-7 day group (P =0.0392) and a significant difference between the 4-7 day group and the more than 8 days group (P =0.0003).Conclusions The early manifestations of COVID-19 in children with abnormal imaging are mostly small subpleural nodu-lar ground glass opacity.The changes on the Delta-variant COVID-19 chest CT were milder than the original strain.The lesions reached a peak on CT in 4-7 days and quickly improved and absorbed after a week.Dynamic CT re-examination can achieve a good prognosis.