Lung cancer is among the most commonly diagnosed malignancies in the world, and has a high mortality rate. Squamous cell lung cancer is a relatively common subtype of lung cancer, diagnosed in 20-30% of cases, of which only lung adenocarcinoma is more commonly diagnosed. Patients with squamous cell lung cancer do not show uniformity in clinical outcome, and are treated in the same way, regardless of morphological subtype. Because the profile of gene variants, as well as the specific profile of gene expression, is still not fully elucidated in this type of tumor, patients are still mostly treated with systemic chemotherapy. It is hypothesized that better molecular characterization of squamous cell lung cancer by biological characteristics could lead to a personalized approach to patient treatment, better prediction of response to therapy, and ultimately a better treatment outcome for this type of tumor. Therefore, further research is needed that will contribute to better molecular characterization of this type of tumor. The aim of this doctoral dissertation is to analyze and understand the expression profile of mRNA, protein and miRNA molecules in squamous cell lung cancer with the ultimate goal of identifying key molecules in the tumorigenesis of this disease.