Inhalation injury (INHI) is defined as an acute airway injury caused by inhalation of hot steam and/or products of combustion. Mortality in patients with INHI is often associated with the development of secondary complications such as extensive infections, pneumonia, direct mucosal damage, mucosal sloughing, and obstructions. Currently, it is acknowledged that the major problem lies in the lack of uniformity in diagnosis, grading, and treatment. The investigation of specific biomarkers for INHI has a great potential to address this issue. Such biomarkers could serve not only to unify diagnosis and treatment, but also to predict the development of secondary complications in patients with INHI. Due to the rarity of the injury, this complex project was designed as a prospective study with the aim of monitoring individual patient parameters during hospitalization. Samples of several matrices (buccal and oropharyngeal swabs, bronchoalveolar lavage - BAL, urine, and blood) for subsequent analyses are collected at 6 time points. In my thesis, I focus on the molecular biological aspects of INHI. Therefore, the main aims are: i) to determine the microbiome and antibiotic resistance genes in samples from upper and lower airways, blood, and/or urine of patients with INHI and with/without infectious complications during their hospitalization; and ii) to select miRNA correlating with INHI using RNAseq analysis in BAL and urine samples, and iii) to characterize toxic compound in BAL and urine.