The popularity of electronic cigarettes (e-cigarettes) is rapidly increasing in many countries. These devices are designed to imitate regular cigarettes, delivering nicotine via inhalation without combusting tobacco but currently, there is a lack of scientific evidence on the presence or absence of nicotine exposure. Such research relies on evidence from e-cigarette users urine samples. In this study, we aimed to determine the levels and compare the amount of nicotine to which e-cigarette users, cigarette smokers and passive smokers are exposed. Therefore, urine samples were collected from e-cigarette users, cigarette smokers, passive smokers, and healthy nonsmokers. The urinary cotinine levels of the subjects were determined using gas chromatography-mass spectrometry. The mean (+/- SD) urinary cotinine levels were determined as 1755 +/- 1848ng/g creatinine for 32 e-cigarette users, 1720 +/- 1335ng/g creatinine for 33 cigarette smokers and 81.42 +/- 97.90ng/g creatinine for 33 passive smokers. A significant difference has been found between cotinine levels of e-cigarette users and passive smokers (p<0.05). There were no statistically significant differences between e-cigarette users and cigarette smokers (p>0.05). This is a seminal study to demonstrate the e-cigarette users are exposed to nicotine as much as cigarette smokers.