Objective:Apoptosis plays a critical role in carcinogenesis. Intracellular proteases known as caspase-9 directly or indirectly play roles inactivating apoptosis. In this study, we aimed to investigate the effect of caspase-9 level in lung skuamous cancer tumor tissues on lymph node metastasis, clinicopathologic parameters and prognosis. Material and Methods: The study included 50 patients diagnosed with squamous cell lung cancer. The caspase-9 level in the tumor and metastatic lymph nodes was assessed using real time-polymerase chain reaction( RT-PCR) methods. Results: The median age of the patients was 61 years (range, 54-68 years). All patients were men and smokers. The average duration of follow-up was 50.26±39.21 months, and progression-free survival was 26.34±19.50 months. Among 50 patients, 22 (44%) had lymph node metastasis. The caspase-9 level was studied in tumors with and without lymph node metastasis. Moreover, the caspase-9 levels in tumors with lymph node metastasis were statistically and significantly lower than tumors without lymph node metastasis (p<0.001). The caspase-9 level decreased as the stage increased (p<0.001). In the presence of angiolymphatic invasion and poorly differentiated tumor tissue, a low level of caspase-9 was identified. Conclusion: The caspase-9 level decreased with increasing stage and the presence of lymph node metastasis. No statistically significant association was detected between caspase-9 and survival. A literature review revealed that no studies have evaluated the correlation between caspase-9 in the squamous cell subtype, clinicopathological parameters, and survival. Extensive studies involving a significant number of patients are required to determine the prognostic and predictive significance of the caspase-9 level in our population.