Several studies have investigated the relationship between traits of personality and smoking behaviours. An essential feature of a healthy personality is to be able to self-regulate behaviour and, in so doing, to feel in control. Addiction is accompanied by a lack of this feeling. The extent to which an individual attributes the effects of events to him/herself or to the environment is called locus of control. However, to our knowledge, no investigation of locus of control and smoking phenotypes has been conducted. This study will assess the association between locus of control, assessed in 8 year old children and 16 year old teenagers, with smoking behaviour at the age of 20.