Abstract: Objective: This study aimed to investigate the chest computed tomography (CT) findings of SARS-CoV-2 Omicron variants in elderly patients with underlying diseases. Methods: We retrospectively analyzed data from 140 elderly patients with underlying diseases who were infected with SARS-CoV-2 Omicron variants. The patients were divided into a moderate group and a severe/critical group based on their clinical classifications. Clinical data, laboratory results, and chest CT data (including lesion distribution, morphology, image signs, and lung lobe score) were collected and analyzed for all patients. Results: Hypertension and hyperlipidemia were the most prevalent underlying diseases among elderly patients with the Omicron variant of SARS-CoV-2. Ground-glass density opacity was the main chest CT manifestation, typically presenting as a mixed distribution across multiple lung lobes. Common clinical symptoms include fever, cough, and sputum production. The proportion of patients with fever was significantly higher in the severe/critical group compared to the moderate group. Additionally, the lymphocyte count was higher in the moderate group compared to the severe/critical group, while the procalcitonin level was significantly higher in the severe/critical group. Pleural thickening was also more prevalent in the severe/critical group. The right inferior lobe score was the highest in both groups (2 (1,3) and 3 (2,4) for moderate and severe/critical groups, respectively), with the total score and individual lobe scores being significantly higher in the severe/critical group. Conclusions: Chest CT scans play a crucial role in classifying disease severity and evaluating disease progression in elderly patients with underlying diseases infected with the Omicron variant of the novel coronavirus. These findings can also guide clinical treatment decisions.