Objective: To explore the characteristics of high-resolution computed tomography (HRCT) in diabetes complicated with coronavirus disease 2019 (COVID-19)-associated pneumonia. Materials and Methods: This study included 584 patients (359 males and 225 females), aged between 60~99 years old (mean, (76±9) years), with positive chest computed tomography (CT) findings and diagnosed with COVID-19 in our hospital from December 14, 2022, to January 10, 2023. Of these, 225 patients were diabetic and 359 were non-diabetic. The features of the chest HRCT from patients with diabetes mellitus complicated with COVID-19 and those without diabetes mellitus complicated with COVID-19 were compared. Moreover, 363 patients in the acute stage of COVID-19 (defined as the time interval between onset and CT examination <7 days) were selected for subgroup analysis, and the HRCT characteristics of COVID-19 between the diabetes group and the non-diabetic group in the acute stage. Results: The location, distribution, morphology, and concomitant signs of pulmonary lesions between the two groups of patients with COVID-19 did not differ significantly. Conversely, statistically significant differences in density (fine mesh, uneven density) and lesion margin (fuzzy lesion margin) were detected. In particular, the grid, uneven, and fuzzy signs on lung imaging were significantly higher in the non-diabetic group than that in the diabetic group. Additionally, 54 patients (24%) in the diabetic group and 127 patients (35.38%) in the non-diabetic group demonstrated fine mesh shadows. There were 181 patients (80.44%) in the diabetic group and 313 patients (87.19%) in the non-diabetic group with uneven density. Furthermore, 205 patients (91.11%) in the diabetic group and 344 patients (95.82%) in the non-diabetic group had blurred edges. There was significantly less pulmonary grid shadowing in the acute subgroup with diabetes (35, 24.65%) than in the acute subgroup without diabetes (82, 37.10%). Conclusion: The features of chest HRCT in patients with diabetes mellitus and COVID-19 are mainly exudation, uniform density, and a clear edge, while the interstitial changes are not obvious compared with patients in the non-diabetic group.