OBJECTIVE: Our study aims to quantify post-Coronavirus disease-2019 (COVID-19) pneumonia-related pulmonary fibrosis using high resolution computed tomography (HRCT) scoring and assess its correlation with clinical parameters, lymphocytes, mean platelet volume (MPV), and lymphocyte/monocyte ratio (LMR). Early detection and understanding of fibrosis progression in patient subsets are essential for enhancing post-COVID-19 patient outcomes. MATERIAL AND METHODS: This retrospective, single-center study aims to quantify post-COVID-19 pneumonia pulmonary fibrosis using HRCT scoring and explore its associations with clinical parameters, lymphocytes, MPV, and LMR. From March 1, 2020, to December 31, 2021, HRCT reports of patients diagnosed with COVID-19 within 14 days of symptom onset were reviewed. Those with COVID-19 pneumonia were identified, and subsequent HRCTs performed 2 months or later post-infection were analyzed for fibrosis. Data on demographics, hospitalization details, and laboratory findings were collected. Fibrosis scores were determined using quantitative HRCT. RESULTS: A total of 133 patients (60.2% male, mean age 57.3) were included. Of these patients, 50.4% were hospitalized. Quantitative HRCT analysis indicated average fibrosis of 2.7% (range: 0.9-28.7%). Lower lymphocyte counts correlated significantly with increased fibrosis ( CONCLUSION: This study underscores the importance of monitoring lymphocyte counts in COVID-19 patients for early detection of pulmonary fibrosis. The findings suggest a need for screening and prompt diagnosis of fibrosis post-COVID-19, particularly in patients with lymphopenia. Further research using quantitative HRCT could enhance understanding and management of progressive interstitial lung diseases, especially in the context of future pandemics.