AIM To investigate the diagnostic and prognostic significance of pro-gastrin-releasing peptide (ProGRP) in non-small cell (NSCLC) and small cell lung cancer (SCLC) and compare this marker with other known serum markers in lung cancer. PATIENTS AND METHODS Serum levels of ProGRP, neuron-specific enolase (NSE), CYFRA 21-1 and carcinoembryonic antigen (CEA) were measured in 37 patients with benign pulmonary disease (BPD), 88 with advanced NSCLC and 37 with SCLC. RESULTS The ProGRP assay showed a better clinical performance than that of NSE in discriminating between SCLC and BPD or NSCLC, especially at specificity higher than 90%. ProGRP and NSE sensitivity in SCLC at 95% specificity versus the BPD group was 78.4% and 48.6%, (p=0.001) and at 97.7% specificity versus NSCLC, 75.7% and 37.8%, respectively (p=0.001). A significant association of low ProGRP levels with high-grade NSCLC tumors was found (p=0.002). A univariate analysis showed a significant association of ProGRP with survival both in NSCLC and SCLC (p=0.03 and p=0.04, respectively). In multivariate analysis, performance status (PS) and CYFRA 21-1 in NSCLC, and PS, CYFRA 21-1 and serum lactic dehydrogenase in SCLC were found as significant variables with an independent impact on survival. CONCLUSION ProGRP is a useful marker in SCLC, with diagnostic performance better than that of NSE and demonstrating association with survival in NSCLC and SCLC limited to univariate analysis.