The aim is to identify the source of sexuality education used during childhood and adolescence and to analyse whether this education influences their sexual attitudes, their ability to cope with unwanted situations they experience and their satisfaction with their sexual lives. This is a non-experimental, quantitative, ex post facto, cross-sectional study. The sample is formed of 675 young people, with 50% of the ages included being between 20 (Quartile 1) and 22 (Quartile 3) years. The data collection was done by means of an online questionnaire, including sociodemographic and Likert questions about their sex life. Fisher “Independence Contrasts”and correlations were used to see and quantify the relationship among the variables. The main source of education was pornography (29.3%) and the internet (12.4%). The source of education has a significant relationship with whether the use of contraceptives is accepted or not (p< 0.001), refusal to use contraceptives (p< 0.001), engaging in risky sexual practices (p< 0.001), facing unwanted sexual situations (p< 0.001) and dissatisfaction with their sex life (p< 0.001). It is necessary that children and adolescents have sex education in safe environments, such as in a home or school setting, and the school nurse plays a vital part in this education. This would reduce the need for adolescents and young people to use the internet and pornography as a source of education. School nurses should be the educational axis to offer children and adolescents a reliable point of information about sex education. A joint work with teachers, nurses, students and parents would contribute positively to reduce the number of risky situations young people are facing, and it would promote and improve healthy attitudes towards sex and interpersonal relationships.