Platelet-derived microparticles (PDMP) play an important role in the pathogenesis of diabetic vasculopathy, and statins or eicosapentaenoic acid (EPA) have been shown to have a beneficial effect on atherosclerosis in hyperlipidemic patients. However, the influence of EPA and statins on PDMP and adiponectin in atherosclerosis is poorly understood. We investigated the effect of pitavastatin and EPA on circulating levels of PDMP and adiponectin in hyperlipidemic patients with type II diabetes. A total of 191 hyperlipidemic patients with type II diabetes were divided into three groups: group A received pitavastatin 2 mg once daily (n = 64), group B received EPA 1800 mg daily (n = 55) and group C received both drugs (n = 72). PDMP and adiponectin were measured by ELISA at baseline and after 3 and 6 months of drug treatment. Thirty normolipidemic patients were recruited as healthy controls. PDMP levels prior to treatment in hyperlipidemic patients with diabetes were higher than levels in healthy controls (10.4 +/- 1.9 vs. 3.1 +/- 0.4 U/ml, p < 0.0001), and adiponectin levels were lower than controls (3.20 +/- 0.49 vs. 5.98 +/- 0.42 microg/ml, p < 0.0001). PDMP decreased significantly in group B (before vs. 6M, 10.6 +/- 2.0 vs. 8.0 +/- 1.7 U/ml, p < 0.01), but not in group A (before vs. 6M, 9.4 +/- 1.9 vs. 9.6 +/- 1.7 U/ml, not significant). In contrast, group A exhibited a significant increase in adiponectin levels after treatment (before vs. 6M, 3.29 +/- 0.51 vs. 4.16 +/- 0.60 microg/ml, p < 0.001). Furthermore, group C exhibited significant improvement in both PDMP and adiponectin levels after treatment (PDMP, before vs. 6M, 11.2 +/- 2.0 vs. 4.5 +/- 2.7 U/ml, p < 0.001; adiponectin, before vs. 6M, 3.24 +/- 0.41 vs. 4.02 +/- 0.70 microg/ml, p < 0.001). Reductions of PDMP in combined therapy were significantly greater than those observed with EPA alone (p < 0.05 by ANOVA). In addition, soluble CD40 ligand exhibited almost the same change as PDMP in all therapy groups. These results suggest that pitavastatin possesses an adiponectin-dependent antiatherosclerotic effect, and this drug is able to enhance the anti-platelet effect of EPA. The combination therapy of pitavastatin and EPA may be beneficial for the prevention of vascular complication in hyperlipidemic patients with type II diabetes.