A retrospective study examined bronchoalveolar lavage fluid (BALF) in 100 patients, 65 of whom had lung cancer. In patients with lung cancer, higher concentrations of tumor markers and cytokines (except IL-10) were detected in BALF compared to the control group. ctDNA was detected more frequently in BALF than in blood and with higher concordance with tissue genotyping. Immune profiling revealed changes in immune cell composition in BALF in lung cancer. Advanced cancer stage, high IL-6/IL-10 ratio and low CD8+/Treg ratio in BALF were associated with worse survival. The study suggests that BALF may serve as a minimally invasive method for the diagnosis and prognostic assessment of lung cancer.