Background and Objectives: COVID-19 infection may influence many physiological processes, including glucose metabolism. Acute hyperglycaemia has been related to a worse prognosis in patients with severe COVID-19 infection. The aim of our study was to find out if moderate COVID-19 infection is associated with hyperglycaemia.Materials and Methods: A total of 235 children were enrolled in the study between October 2021 and October 2022, 112 with confirmed COVID-19 infection and 123 with other RNA viral infection. In all patients, types of symptoms, glycaemia at the time of admission, and basic anthropometric and biochemical parameters were recorded.Results: Average glycaemia was significantly higher in COVID-19 patients compared to other viral infections (5.7 ± 1.12 vs. 5.31 ± 1.4 mmol/L,p= 0.011). This difference was more obvious in subgroups with gastrointestinal manifestations (5.6 ± 1.11 vs. 4.81 ± 1.38 mmol/L,p= 0.0006) and with fever (5.76±1.22 vs. 5.11±1.37 mmol/L,p= 0.002), while no significant difference was found in subgroups with mainly respiratory symptoms. The risk of hyperglycaemia (>5.6 mmol/L) was higher in COVID-19 patients compared to other viral infections (OR = 1.86, 95%CI = 1.10–3.14,p= 0.02). The risk of hyperglycaemia was significantly higher in COVID-19 compared to other viral infections in the subgroups of patients with fever (OR = 3.59, 95% CI 1.755–7.345,p= 0.0005) and with gastrointestinal manifestations (OR = 2.48, 95% CI 1.058–5.791,p= 0.036).Conclusion: According to our results, mild hyperglycaemia was significantly more common in children with moderate COVID-19 infection compared to other RNA virus respiratory and gastrointestinal infections, especially when accompanied by fever or gastrointestinal symptoms.