The present study aimed to determine whether either of two calcium channel blockers affected urinary albumin excretion or urinary levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and liver-type fatty acid-binding protein (L-FABP) in hypertensive diabetic patients with chronic kidney disease (CKD) who were already being treated with maximum doses of the angiotensin II receptor blocker olmesartan. We conducted an open-label, randomized, parallel-controlled study on type 2 diabetic patients with stable glycemic control who were receiving fixed doses of antidiabetic agents. The patients received either 8 mg per day azelnidipine, which was increased up to 16 mg per day (azelnidipine group; n=34), or 2.5 mg per day amlodipine, which was increased up to 5 mg per day (amlodipine group; n=33), over a 24-week period. Mean systolic and diastolic blood pressure decreased significantly in both groups, but there was no significant difference between the two groups at the end of the study. Serum creatinine levels and estimated glomerular filtration rate did not differ significantly between the two groups, whereas the urinary albumin/creatinine ratio and 8-OHdG and L-FABP levels decreased significantly in the azelnidipine group compared with the amlodipine group. Plasma aldosterone level was significantly decreased in the azelnidipine group, and its changes correlated significantly with those of urinary 8-OHdG and L-FABP. Our results suggest that the addition of azelnidipine to the maximal recommended dose of olmesartan was more effective in reducing albuminuria and oxidant stress in hypertensive diabetic patients with CKD than the addition of amlodipine.