We reviewed the literature on ambulatory blood pressure (BP) monitoring in type 2 diabetes mellitus (T2DM) (focusing on organ damage progression, prognosis, white coat hypertension, and masked hypertension) and metabolic syndrome (MetS). In the text we reported 21 articles about T2DM and 11 about MetS, part of which were included in meta-analyses. In T2DM, individual studies and meta-analyses indicate that 24-h pulse pressure and reduced night-time BP fall or reverse dipping predict organ damage progression, total cardiovascular events and all-cause mortality. Moreover, white coat hypertension seems to be less frequent in T2DM and its impact on cardiovascular complications remains controversial. In contrast, masked hypertension is more frequent in T2DM and seems to be associated with increased organ damage. Some studies reported higher ambulatory BP in patients with MetS, but these patients were older and had higher clinical BP than those without MetS. With regard to the circadian BP profile, contrasting data have been reported, although pooled data suggest a higher risk of nondipping in patients with MetS.