BACKGROUND COPD is an epidemic of modern society. It is one of the major causes of morbidity and mortality in the world. It is a well-known thought that one of the main complication of COPD is Pulmonary Embolism. It is mainly because of changes in platelet count and morphology under the chronic influence of inflammatory cytokines. [1,2,3] Meanwhile, this can also be taken as a parameter for determining severity of COPD. [4] MATERIALS AND METHODS The descriptive study of 200 patients diagnosed with COPD, admitted in General Medicine Wards at Government Rajaji Hospital, Madurai were selected. Mean platelet volume [5] of each patient was found out with 24 hours of admission. Spirometry was done to assess the severity of COPD and correlation was established between the two. Statistical Analysis-Correlation coefficient. Settings and Design-Correlation study. RESULTS From the study, it was found that COPD is more common after 40 years in males, and is strongly associated with smoking. It was also found that there is a strong correlation between spirometry values and mean platelet volume, i.e. when FEV1% and FEV1/ FVC ratio decreases, the MPV also decreases and when FEV1% and FEV1/FVC ratio decreases, the platelet count increases. CONCLUSION MPV was significantly decreased in patients with acute exacerbation of COPD [6,7,8] when compared with stable phase of COPD. FEV1, FEV1/ FVC are the main parameters in PFT [9] to determine the severity. MPV in patients with COPD was found to be independent of age, sex, family history, COPD, systemic hypertension and diabetes mellitus. While smoking is an important risk factor. When MPV decreased in severe COPD, platelet count increased. [10] MPV can be used as a prognostic marker for COPD. There was high negative correlation between platelet count and MPV. [11] There was a very high positive correlation between MPV and severity of COPD.