Masked hypertension is associated with an increase in cardiovascular risk. Mean platelet volume (MPV), a determinant of platelet function, is a new risk factor for atherothrombosis. High-sensitive C-reactive protein (CRP) is an exquisitely sensitive systemic marker of inflammatory response. We designed this study to evaluate MPV and CRP in masked hypertensive patients and to compare those with essential hypertensive and healthy normotensive individuals. Forty-two untreated masked hypertensive patients, 53 untreated essential hypertensive patients and age-sex matched 37 normotensive healthy individuals were included in the study. Blood samples were collected and haematological parameters were measured. Plasma CRP level was measured by immunonephelometery method. The MPV was significantly higher in masked hypertensive (8.8 +/- 1.6 fl) and essential hypertensive patients (9.1 +/- 1.7 fl) than those of normotensive control individuals (7.8 +/- 0.8 fl) (P=0.01 and P=0.003, respectively), whereas there was no significant difference between the masked hypertensive and essential hypertensive individuals (P>0.05). CRP levels were also significantly higher in masked hypertensive patients than in normotensives individuals (3.31 +/- 1.70, 1.98 +/- 1.56 mg/l, P<0.001, respectively). There was a significant positive correlation between MPV and CRP levels (P<0.001, r=0.850) in masked hypertensive patients. Patients with masked hypertension have higher MPV and CRP values than controls. Increased MPV and CRP levels may be the possible mechanisms behind the increased cardiovascular risk in masked hypertensive patients. Blood Coagul Fibrinolysis 24:170-174 (C) 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins.