Aims: Higher mean platelet volume (MPV) in diabetic patients has been considered as an emerging risk factor for diabetes related micro- and macrovascular complications. Human paraoxonase 1/arylesterase (PON1), which has antioxidant and antiatherogenic properties, is documented in high oxidative stress conditions like uncontrolled diabetes. The present study aimed to evaluate the relationship between mean platelet volume (MPV) and paraoxonase-1 (PON-1) activity, brachial artery diameter (BAd) and intima media thickness (BA-IMT), in diabetic patients with regard to obesity and diabetic complications.Methods: Two-hundred and one diabetic patients (mean age: 52.4 ± 13.4 years, 73.6% females) were grouped according to obesity and diabetic complications (microvascular and macrovascular). Data on demographics, anthropometrics, diabetic complications, MPV levels, BAd and BA-IMT, and serum paraoxonase and arylesterase activities were recorded. The correlation of MPV values to paraoxonase and arylesterase activities, BAd and BA-IMT was evaluated.Results: Paraoxonase and arylesterase values were 119.8 ± 37.5 U/L and 149.0 ± 39.9 U/L, respectively, with no significant difference in respect of obesity and macrovascular complications. Significantly lower values for paraoxonase (107.5 ± 30.7 vs. 123.9 ± 38.8 U/L, p = 0.007) and arylesterase (132.1 ± 30.2 vs. 154.7 ± 41.2, U/L, p = 0.001) were noted in patients with microvascular complications. MPV values were 9.10 ± 0.87 fL, with no significant difference across the groups and no significant correlation with other parameters.Conclusion: In conclusion, PON-1 activity is more significantly decreased in diabetic patients with microvascular than macrovascular complications with no effects on MPV values. On the other hand, no relationship was found between thrombogenic activity and PON-1 activity, BAd and BA-IMT regardless of obesity and diabetic complications.