The consumption of e-cigarettes has rapidly increased in the last years, both worldwide and in Poland, especially among adolescents and youth. Many e-cigarette users also smoke conventional cigarettes ("dual use"). Some researchers argue that e-cigarette vaping, where tobacco burning seems to be eliminated, significantly reduces the number and content of toxic substances when compared to combustible tobacco products. They also underline that consumption of less harmful tobacco and nicotine products can substantially reduce the health consequences of tobacco smoking when the cigarette smoking would be substituted by the e-cigarette use. However, the number of studies that prove negative health consequences of e-cigarette use is steadily increasing. Many carcinogenic, cardiovascular and pulmonary toxic compounds were found in e-cigarettes and, dependently on the patterns of e-cigarette use, their content may increase to the level observed for cigarette smoking. Studies prove that dual use of e-cigarettes and manufactured cigarettes is more risky than cigarette smoking. Therefore, there is an urgent need to regulate e-cigarettes as strictly as tobacco products.