Aim: Chronic rhinosinusitis (CRS) is characterized by persistent inflammation of the nasal and paranasal sinus mucosa. The pathogenesis of chronic sinusitis is not yet clearly understood. Recently, mean platelet volume (MPV) has been known as a simple inflammatory marker in inflammatory diseases. The aim of this study was to investigate the levels of hematological parameters such as red blood cells (RBC), haemoglobine (Hb), haematocrit (Htc), white blood cells (WBC), platelet (PLT), and mean platelet volume (MPV) in patients with CRS without nasal polyposis. Method: After overnight fasting, peripheral venous blood samples were taken from patients with CRS and control groups. We measured the complete blood count (CBC) parameters in a blood sample collected in etilendiamintetraasetik asit (EDTA). Laboratory data were screened via hospital’s computerised database. Result: CRS group consisted a total of 90 patients, 34 (38%) male and control group consisted 90 patients, 44 (49%) male. WBC, RBC, Hb and Htc levels were similar in patient and control groups. However, PLT level was borderline higher in CRS group compared to control group (284±87 vs 253±59, P=0.06) and MPV level was significantly higher in CRS group compared to control group (8.0±0.9 vs 7.3±0.9, P<0.001). Conclusion: As CRS is a chronic inflammatory disorder, we believe that platelets have a role in CRS. If MPV value is an indicator of inflammation, increased MPV values may be associated with CRS.