Here we conducted a population-based candidate polymorphism association study and genotyped ACE (I/D), NOS3 (rs2070744, rs1799983), SERPINE1 (rs1799768), PLAU (rs2227564) and PLAUR (rs344781, rs2302524) polymorphisms in hospitalized patients with confirmed COVID-19, evaluating their association with the percentage of lung involvement on computerized tomography (CT) scans. This evidence concerns the gene NOS3 and COVID-19.