OBJECTIVES: Adiponectin is a novel plasma protein produced exclusively in adipocytes. Despite early data, its relationship with obesity and diabetes has been recently questioned. Since plasma lipids influence diabetes and obesity, of concern is whether any associations between plasma lipids and adiponectin exist. DESIGN AND METHODS: The aim of this study was to measure adiponectin levels and to investigate their associations with plasma cholesterol fractions and triglycerides in 73 obese non-diabetic subjects (44 women and 29 men), and 43 obese diabetic subjects (28 women and 15 men), aged 52.7 +/- 11.2 and 53.1 +/- 11 years, respectively, and matched for age, sex and BMI. The WHO definitions of obesity and diabetes were used. Adiponectin was determined by an enzyme-linked immunosorbent assay. RESULTS: No correlations between adiponectin and total and LDL cholesterol levels were shown (for the whole cohort: r=0.0130; p=0.8899, and r=0.0807; p=0.3958, respectively). A positive correlation between HDL cholesterol levels and adiponectin occured predominantly in obese women without diabetes (r=0.4531; p=0.0023), resulting in an overall statistical trend in the whole cohort (r=0.2243; p=0.0164). A negative correlation between serum adiponectin and triglycerides was found (r=-0.3413; p=0.0002). CONCLUSION: Adiponectin correlated only with TG and partially with HDL but not with LDL and total cholesterol in the study group of obese diabetic and obese non diabetic subjects. In view of these results we suggest that the role of adiponectin in human metabolism is unclear and merits further investigation.