The use of electronic cigarettes (e-cig) or personal vaporizers (PV) has increased in recent years, especially among adolescents and adults, increasing risk factors for their health or being a starting point for other risk behaviours. The aim of our study is to learn the knowledge, attitudes and behaviours of the adolescent and young adult population on the use of e-cigarettes or PVs. A cross-sectional descriptive study was carried out among 375 subjects. The use of e-cigs or PVs was measured using a self-administered questionnaire. Overall, 13.33% of the respondents used e-cigarettes or PVs. A correlation could be established between vape use and age, with 14–18-year-olds being the highest users (25.9%). Additionally, 90.13% of the respondents answered that e-cig or PV use was harmful to health. Other behaviours, such as consumption of energy drinks (ED), increases the probability of vaping by 3.08 times (CI = 1.55–6.29; p = 0.001). Subjects aged 23–26 years and 27–34 years are less likely to vape than subjects aged 14–18 years (OR = 0.31: CI = 0.09–0.96; p = 0.044; OR = 0.07: CI = 0.00–0.63; p = 0.037). The same applies to subjects with secondary education (OR = 0.17: CI = 0.04–0.66; p = 0.011) and postgraduate education (OR = 0.07: CI = 0.06–1.19; p = 0.043), than subjects with primary education. The use of e-cigs and PVs starts at an early age, despite the known harmful effects of e-cigs and PVs. Their use may occur mainly in recreational situations and in association with other substances such as ED.