Background: Pleural effusion results from either malignant or nonmalignant conditions, cytological examination of pleural fluid is diagnostic only in about 50% of malignant pleural effusions. Cancer ratio (serum serum lactate dehydrogenase (LDH)/pleural adenosine deaminase (ADA) may be helpfull in cancer diagnosis of patients with exudative pleural effusion, we investigated this issue along with CEA ratio (pleural CEA/serum CEA) Methods: This study included 60 patients referred to Clinical Oncology & Nuclear Medicine and Chest Departments Menoufia University hospital in the period from January 2016 to January 2017 presented with exudative pleural effusion the mean age was 67.20 + 11.12. 33 patients out of 60 were males and 27 were females, patients were classified into 3 groups, group I included 20 patients with malignant plueral effusion, group II included 20 patients with tuberculous pleural effusion and group III included 20 patients with parapneumonic pleural effusion. The cancer patients group included stage IV disease: 10 patients had bronchogenic carcinoma, 2 patients had pleural mesothelioma, 5 patients had breast cancer and 3 patients with ovarian cancer. All patients underwent thoracentesis and cytology, Serum LDH, pleural ADA, serum and pleural CEA were done then data was statistically analyzed and the cut off value for cancer ratio and CEA ratio was done Results: Cancer ratio was significantly higher in the patients with malignant pleural effusion 59.32 ± 8.19 than the tuberculous group 5.72 ± .15 than patients with parapneumonic effusion 10.30 ± .79, (p < 0.001). CEA ratio was significantly higher in malignant group 4.17 ± .47 than parapnemonic group 2.88 ± .27 than tuberculous group 1.16 ± .08, (p < 0.001). 1 year survival in all patients was (86.6%) and in cancer patients group (80%), there was no statistically significant difference in survival between different primary cancer sites (P > 0.05). in all groups, the mean cancer ratio 19.8188 ± 3.41536 in survived patients compared with 59.5548 ± 18.51138 in non survived patients, the difference was significant (p < 0.01), also the mean CEA ratio 2.4238± .22462 in survived patients compared with 4.8050± .78987 in non survived patients (p < 0.01). Furthermore cancer ratio at cut off point (5.03) can discriminate malignant pleural effusion with sensitivity of 100% and a specificity of 87% while CEA ratio can detect malignant pleural effusion at cut off point (2.53) with sensitivity of 75% and a specificity of 40% Conclusions: Cancer ratio at cut off point (5.03) is a simple method which can discriminate malignant pleural effusion with sensitivity of 100% and a specificity of 87%. Legal entity responsible for the study: menoufia university Funding: None Disclosure: All authors have declared no conflicts of interest.