Exhaled breath condensate (EBC) has recently emerged as a non-invasive sampling method for real-time analysis and evaluation of oxidative stress biomarkers in the lower respiratory tract airways, especially in various lung diseases including asthma, chronic obstructive pulmonary disease, and lung cancer. In particular, endothelin-1 and interleukin-6 have been found to be elevated in the EBC from patients with lung cancer. Therefore, the current study aims to evaluate the temporal changes of various oxidative stress biomarkers and cytokines in EBC and blood in patients with NSCLC who are undergoing surgical lung resections and the potential role of these parameters in predicting subsequent tumour recurrence. Also, the correlation of biomarkers in blood or EBC with lung tumour tissue will be looked into.