Pleural effusion (PE) is a common clinical problem, etiologically, difficult to diagnose, requiring invasive procedures. During last years, serum neutrophil-lymphocyte ratio (NLR) has been investigated as a new inflammatory marker. The aim was to evaluate serum NLR in differential diagnosis between tuberculous (TB) and malignant pleural effusions (MPEs). Material and methods. A retrospective study included adults, diagnosed with PE and hospitalized in Constanta Pulmonology Clinic, between March 2017 and September 2018. Biomarkers were collected from serum and pleural fluid. Final diagnosis of malignancy was assessed by pleural fluid cytology and/or pleural biopsy. The evidence of Mycobacterium tuberculosis in smears or culture from pleural fluid or caseous granulomatous specific lesions in pleural biopsy samples were considered suggestive for TB etiology. Results: 463 cases were divided into 110 MPEs and 353 TBPEs. NLR increased in both categories of patients, mainly in malignancy group (p=0.001). Conclusions: serum NLR seems to be useful in evaluating the etiology of malignant or TB pleural effusions.