Introduction and objective: In recent years, electronic nicotine delivery systems (ENDS) have gained popularity as an alternative to traditional cigarettes. While the impact of conventional smoking on the oral microbiota is well documented, the influence of e-cigarettes on upper respiratory tract (URT) microbiota and diseases, such as asthma or chronic obstructive pulmonary disease (COPD), remains poorly understood. The aim of this study is to analyze available research on the effects of ENDS on the composition and function of the URT microbiota. Review methods: A literature review was conducted using the PubMed database, with publications selected based on relevant keywords. Additionally, the study was supplemented with statistical data from Polish and international sources (Gov, WHO, FDA). Brief description of the state of knowledge: In Poland, the number of e-cigarette units sold in 2023 reached 100 million. The ENDS aerosol can significantly disrupt the microbial balance, increasing the number of pathogenic microorganisms. Various chemical substances, such as nicotine, heavy metals, and aldehydes, may damage mucosal membranes, induce oxidative stress, and increase the production of pro-inflammatory cytokines, ultimately contributing to the development of numerous respiratory pathologies. Exposure to the aerosol significantly contributes to the exacerbation of asthma attacks and increases the risk of developing chronic obstructive pulmonary disease (COPD). Summary: Current research indicates that regular use of END -both active and passive—can lead to dysbiosis of URT, increasing the risk of developing respiratory diseases. Unfortunately, the diversity of ENDS types and the complexity of their design hinder the interpretation of research findings. Moreover, there is a lack of significant data regarding the longterm health effects of electronic nicotine delivery systems.