Purpose: This study aimed to assess COVID-19''s effects on vascular inflammatory response, by evaluating 18-Fluorodeoxyglucose (18F-FDG) uptake via positron emission tomography/computed tomography (PET/CT) in the artery of diffuse large B cell lymphoma (DLBCL) patients before and after infection with COVID-19.Patients and Methods: Thirty-five DLBCL patients administered the chemotherapy regimen R-CHOP and examined by oncological 18F-FDG PET/CT imaging twice from August 2022 to February 2023 for pre-treatment evaluation or assessment of treatment efficacy were enrolled. Seventeen patients were confirmed with COVID-19 within the study period. Arterial wall FDG uptake was semi-quantitatively analyzed as TBR (target-to-blood pool ratio) in 14 different vascular regions using oncological 18F-FDG PET/CT. Based on COVID-19 course and the two PET/CT scans, we further analyzed time-related FDG uptake for vascular walls in DLBCL patients with COVID-19.Results: Arterial TBRs were higher in the last PET/CT examination than previous ones in all patients with or without COVID-19. Besides the ascending aorta, & UDelta;TBR (last PET/CT scanning''s TBR minus previous PET/CT scanning''s TBR) were not significantly different between the COVID-19 and Control groups. However, cases scanned & LE;30 days from infection had remarkably higher & UDelta;TBRs in comparison with those assessed >30 days post-infection in the COVID-19 group (p<0.05). A moderate inverse correlation was observed between increment Global TBR (last PET/CT scanning''s average TBR value minus previous PET/CT scanning''s average TBR value) and time distance from COVID-19 onset to 18F-FDG PET/CT scan (Spearman''s rho=-0.591, P=0.012). Interestingly, there were no differences of changes of TBR between different purpose of PET/CT examination group.Conclusion: This work firstly suggested vascular inflammation is elevated in the early post-COVID-19 phase in DLBCL cases compared with prolonged post-COVID-19 phase or controls. Increasing attention should be paid to these patients and the protection of their vascular function and complications in early COVID-19.