Objective:To correlate the serum levels of ceruloplasmin (Cp), copper (Cu), and superoxide dismutase (SOD) with pulmonary function tests (PFTs) in non-diabetics (controls) and patients suffering from Type-1 and Type- 2 diabetes.Methods:The comparative cross-sectional study of 348 participants was performed at the Baqai Institute of Diabetes and Endocrinology (BIDE) - Karachi, Pakistan, from February 2019 to September 2020. Individuals having diabetes-related complications, asthma, chronic obstructive pulmonary disease, chest infection, pregnant women and smokers were excluded. A total of 348 participants were included into three groups after signing informed consent. The control group had 107 non-diabetic participants, with an age range of 6 to 60 years. The diagnosed T1D group (n=107) had an age range of 6 to 25 years. While diagnosed T2D group (n=134) had an age range of 26 to 60 years. During the fasting state, anthropometric parameters, blood pressure, spirometry, and a venous blood sample (5ml) were collected to measure serum Cp, serum Cu, serum SOD, and HbA1c levels by using commercially available kits. The SPSS, version 21, was used for data analysis.Results:The reduced FVC (p-value <0.001), FEV1 (p-value <0.001), and PEFR (p-value <0.001) were found in both groups of diabetes. However, the lower levels of serum Cu (p-value <0.001), SOD (p-value <0.001), and significantly increased values of FEV1/ FVC (p-value <0.001) and Cp levels (p-value 0.030) were found only in T2D group as compared to T1D and controls. The study found no significant correlation of PFTs and serum Cp, Cu, and SOD levels in patients suffering from T1D and T2D.Conclusion:Hyperglycemia leads to more non-enzymatic glycosylation of tissue proteins that reflects reduced PFTs and increased Cp; particularly in T2D, which may alter lung tissue’s physiology. Moreover, the study showed no correlation of PFTs with the Cp, Cu, and SOD in patients suffering from T1D and T2D.