OBJECTIVE: To investigate the characteristics of lymphocytes in type 2 diabetic patients with coronavirus disease (COVID-19). METHODS: Patients with COVID-19 admitted to hospital in Wuxi, China from January 29 to March 15 were included in the study. Lymphocytes were measured and recorded at admission and during treatment. Hospitalization days, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid positive days, minimal lymphocyte count, and occurrence time were collected and comparatively analyzed. Correlations between minimal lymphocyte count and hospitalization days as well as SARS-CoV-2 nucleic acid positive days were analyzed. RESULTS: A total of 63 patients were included in the study, with 16 in the diabetic group and 47 in the non-diabetic group. After adjusting for potential confounding factors, we observed lower minimal lymphocyte count (0.67 +/- 0.36 * 10(9)/L vs. 1.30 +/- 0.54 * 10(9)/L, adjusted P = 0.001), earlier occurrence of the minimal lymphocyte count (2.68 +/- 2.33 days vs. 5.29 +/- 4.95 days, adjusted P = 0.042), and longer hospitalization time (20.44 +/- 5.24 days vs. 17.11 +/- 4.78 days, adjusted P = 0.047) in the diabetic group than in the non-diabetic group. There was a negative correlation between minimal lymphocyte count and hospitalization days (R = -0.600, P < 0.05) as well as SARS-CoV-2 nucleic acid positive days (R = -0.420, P < 0.05). CONCLUSIONS: The diabetic group with COVID-19 had lower lymphocyte count, reached the minimal count faster, and had longer hospital stays than the non-diabetic group. Hospitalization days and SARS-CoV-2 nucleic acid positive days were negatively correlated with the minimal lymphocyte count.