This cross-sectional study compared serum lipoprotein (a) [Lp(a)] concentrations in type 1 and type 2 diabetic subjects and examined the determinants of Lp(a) concentrations in both types of diabetes. Serum Lp(a) was measured in 26 type 1 and 107 type 2 diabetic patients and 126 non-diabetic controls. HbA(1c), fasting lipids and urinary albumin were also assayed. Lp(a) concentrations were higher in both type 1 and type 2 diabetic patients compared with controls (P<0.0001 and P<0.0001, respectively), and were higher in type 1 than type 2 diabetic patients (P<0.05). Waist-hip ratio (WHR) was an independent determinant of Lp(a) concentrations in both type 1 and type 2 diabetes.