Our aim was to assess the ambulatory blood pressure monitoring (ABPM) characteristics or patterns in hypertensive patients with diabetes compared with non-diabetic hypertensives. We performed a cross-sectional analysis of a 68,045 patient database from the Spanish Society of Hypertension ABPM Registry, a nation-wide network of >1200 primary-care physicians performing ABPM under standardized conditions in daily practice. We identified 12,600 (18.5%) hypertensive patients with diabetes. When compared with patients without diabetes, diabetic hypertensives exhibited higher systolic blood pressure (BP) levels in every ABPM period (daytime 135.4 vs. 131.8, and nighttime 126.0 vs. 121.0 mm Hg, P<0.001 for both) despite they were receiving more antihypertensive drugs (mean number 1.71 vs. 1.23, P<0.001). Consequently, diabetic patients suffered from lack of control of BP more frequently than non-diabetic subjects particularly during the night (65.5% vs. 57.4%, P<0.001). Prevalence of a non-dipping BP profile (64.2% vs. 51.6%, P<0.001) was higher in diabetic patients. In the other hand, prevalence of 'white-coat' hypertension in diabetic patients was 33.0%. We conclude that there was a remarkably high prevalence of alterations in ABPM in patients with diabetes. Abnormalities in systolic BP, particularly during the night, and in circadian BP pattern could be linked with the excess of BP-related cardiovascular risk of diabetes. A wider use of ABPM in diabetic patients should be considered.