Introduction:
This study aims to characterize the variables associated with smoking initiation in adolescents, including family dimensions and personal variables of academic performance and individual and group behaviours.

Material and Methods:
Cross-sectional epidemiologic study, in which the information was primarily gathered through a self-administered survey of a sample of 306 students from the "Joan Fuster" secondary school in Sueca (Valencia). Variable addressed included tobacco consumption, frequency of consumption, age at onset, sex, age, frequency of alcohol consumption, being or not a grade repeater, and whether the parents were smokers or smoked in front of the adolescents.

Results:
A total of 306 students between 12 and 17 years of age participated, with an average age of 13.44 years. A total of 50.65% were girls. In terms of academic background, 30.4% were grade repeaters. A total of 69.9% declared themselves non-smokers, 18.3% ex-smokers and 11.8% smokers, 58.3% of whom were girls. The mean age of onset of consumption was 12.65 years. Factors significantly associated with smoking were: Grade repeaters were more likely to smoke than non-repeaters (OR = 3.402, 95%CI [1.7, 6.5], p < 0.001). In turn, students who drank alcohol daily, sporadically or if they partied were more likely to smoke than those who did not drink alcohol (OR = 183.63, 95%CI [13.0, 4689.7], p < 0.001), (OR = 5.687, 95%CI [2.8, 11.7], p < 0.001), (OR = 9.412, 95%CI [4.4, 20.2], p < 0.001), respectively. Additionally, students whose parents did not smoke in front of their children or are non-smokers were less likely to smoke (OR = 0.195, 95%CI [0.053, 0.61], p = 0.008), (OR = 0.348, 95%CI [0.169, 0.704], p = 0.004), respectively. As for gender, being male was less likely to be a smoker (OR=0.542, 95%CI [0.298-0.976], p=0.043.

Conclusions:
Tobacco use in adolescents is a vitally important public health problem, with an age of onset that is too precocious. In our population, most of the students surveyed were non-smokers, and among smokers, the majority were girls. The age of onset was below 13 years of age. Female students, students with parents who smoke or who smoke in front of them, alcohol consumers and repeaters are more likely to be smokers in the future. These results offer practical hints to be taken into account in intervention programmes for tobacco prevention and control in this adolescent population.