This study aimed to assess the levels of potentially toxic and carcinogenic compounds in the vapor from 12 brands of electronic cigarettes (e-cigarettes) compared to a reference product, the medicinal nicotine inhalator. The selected compounds included carbonyls, volatile organic compounds (VOCs), tobacco-specific nitrosamines (TSNAs), and heavy metals. The results showed that the levels of these toxicants in e-cigarette vapor were 9 to 450 times lower than in cigarette smoke and were often comparable to trace amounts found in the reference product. The study concluded that substituting tobacco cigarettes with e-cigarettes may significantly reduce exposure to selected tobacco-specific toxicants, supporting the idea that e-cigarettes could be a harm reduction strategy for smokers unwilling to quit. However, further research is needed to confirm these findings and to evaluate the potential health outcomes of short and long-term exposure to these compounds.This study aimed to assess the levels of potentially toxic and carcinogenic compounds in the vapor from 12 brands of electronic cigarettes (e-cigarettes) compared to a reference product, the medicinal nicotine inhalator. The selected compounds included carbonyls, volatile organic compounds (VOCs), tobacco-specific nitrosamines (TSNAs), and heavy metals. The results showed that the levels of these toxicants in e-cigarette vapor were 9 to 450 times lower than in cigarette smoke and were often comparable to trace amounts found in the reference product. The study concluded that substituting tobacco cigarettes with e-cigarettes may significantly reduce exposure to selected tobacco-specific toxicants, supporting the idea that e-cigarettes could be a harm reduction strategy for smokers unwilling to quit. However, further research is needed to confirm these findings and to evaluate the potential health outcomes of short and long-term exposure to these compounds.