The aim of this study is to compare the effects of candesartan and olmesartan on insulin sensitivity-related parameters, before and after antihypertensive therapy. After a 4-week washout placebo period, 194 hypertensive (diastolic blood pressure (DBP) >= 80mmHg and systolic blood pressure (SBP) >= 130mmHg) patients with well-controlled type II diabetes were randomized to receive either 8mg of candesartan once a day (o.d.) or 10 mg olmesartan o.d. and titrated after 1 month to 16 mg candesartan o.d. or 20mg olmesartan o.d., respectively; the treatment period had a 1-year duration. We evaluated body weight, body mass index, SBP, DBP, glycated hemoglobin, fasting plasma glucose, M value, adiponectin (ADN), resistin (r), retinol-binding protein 4, visfatin, vaspin and high-sensitivity C-reactive protein (Hs-CRP) at their baseline values and after 6 and 12 months of treatment. We observed no variation in body weight or glycemic profile for either treatment. SBP and DBP were significantly reduced by both treatments (from 144+/-8/88+/-6 to 126+/-5/77+/-4mmHg by candesartan (P<0.001) and from 145+/-9/89+/-7 to 128+/-7/79+/-5mmHg by olmesartan (P<0.001)) without any difference between them. Retinol binding protein-4, r, and the vaspin value decreased in the candesartan group but not in olmesartan group. The M value, visfatin and ADN increased with candesartan, whereas no significant variations were observed with olmesartan. Both treatments resulted in a similar reduction in Hs-CRP. Although both therapies resulted in similar reductions in blood pressure, candesartan therapy was more effective than olmesartan therapy in improving insulin sensitivity. Hypertension Research (2010) 33, 790-795; doi:10.1038/hr.2010.85; published online 27 May 2010