Study objective. The objective of this study was to investigate PON1 phenotype and genotype in Romanian patients with abdominal obesity. Materials and methods. The study groups consisted of 88 patients with abdominal obesity and 46 subjects with normal waist circumference, matched for age and gender. For each patient, we determined the clinical parameters that may influence PON1 activities. Q192R and L55M polymorphisms analysis in the PON1 gene were performed by PCR-RFLP using specific primers and restriction enzymes. PON1 lactonase, paraoxonase and arylesterase activities were assayed by spectrophotometric methods. Analysis of PON1 genotypes and activities distribution in the obese and non-obese individuals was performed with Med- Calc Software (Version 22.214.171.124). Results. There was no statistically significant difference between obese and controls in regards to age and gender. The study revealed that PON1 activities were not influenced by gender. Of all PON1 activities, only the paraoxonase activity was inversely correlated with age, being significantly reduced in patients with abdominal obesity compared to non-obesity (p=0.009). Abdominal circumference independently influenced only the variation of arylesterase activity (R2=6.5%, p=0.003). Distribution of PON1 genotypes in the study groups was significantly different (p=0.007) only for the Q192R but not for the L55M genotypes. The QR genotype had the highest influence on paraoxonase activity (R2=40.6; p<0.001). The MM genotype had the greatest influence on arylesterase (R2=11.3%, p<0.001) and lactonase activities (R2=7.4%, p<0.001). Conclusions. Q192R genotypes distribution was significantly different in obese patients and the QR genotype influenced greatly the paraoxonase activity. The MM genotype had the most important independent influence on the lactonase and arylesterase activities .