Researchers and institutions have in recent years been showing growing concerns about the use of the Internet among teenagers. Their psychological and behavioural impact often results in risky behaviour, school failure and family problems. Given the interest in the issue at different levels, this work has a dual intention: (1) have data that makes it possible to identify, from a descriptive point of view, the attitudes, perceptions and habits of using the Internet and social networks among adolescents, and (2) to deepen their understanding, thus contributing to the design of strategies for a more rational and healthy use of the Network. On the basis of a survey of the population of schoolchildren in compulsory secondary education in the Galician community, in which a total of 2339 individuals participated, the results obtained show the high degree of internet uptake in the population under study and measure the scale of the problem with empirical data. Although the figures obtained do not justify an alarming attitude, they point to the need for concrete action plans to be put in place immediately.