Although it is known that many factors have prognostic significance in lung cancer, and thrombocytosis is commonly observed in neoplastic diseases, prognostic significance of platelet counts in lung cancer has not yet been adequately clarified. We aimed to examine the platelet counts of 50 patients who were diagnosed as primary lung cancer in our clinic for 2 years and investigate the correlation between thrombocytosis and survey. 50 patients with primary lung cancer were studied for age, sex, platelet count on admission, and time from date of the diagnosis to death between January 2003- January 2005. The number of primary lung cancer patients with platelet count >400x103/L was 11(22%). Although there was a negative correlation between platelet count and survey (R=-0,40, p<0.05), no significant correlation was seen between age, sex, stage, histopathological type and platelet count (p>0.05). In conclusion, it is observed that thrombocytosis was frequently seen in lung cancer, and survival time was significantly low in cases with thrombocytosis. It is suggested that platelet counts can be included in future multifactorial analyses of survival in patients with lung cancer.