Previous research has indicated that young people are under considerable social pressure to take up smoking. This study has therefore sought to explore and better understand the mechanisms through which peer‐related social factors operate to encourage young people to smoke. Individual qualitative interviews were held with adolescent children aged 11–12 years (N=102) within youth clubs based in economically deprived areas of Northern Ireland, and then followed up on two occasions during the subsequent 3 years (N=51/39). The data implied that, although peers influence smoking uptake, this seldom happens through direct persuasion, but rather as the result of the young person striving to conform to the normative behaviour of the peer group with which they identify. The findings are consistent with social identity theory and self‐categorization theory in that for both smoking and non‐smoking 14‐year‐olds smoking activity appears to provide a means through which to define social groups, to accentuate similarity within groups and differences between groups. In‐group favouritism was expressed in the sharing of cigarettes within the in‐group and in the negative stereotyping of out‐group members. There was some evidence that group affiliation may be negotiated differently for boys and girls. These findings imply that successful intervention needs to reconsider the normative processes that encourage young people to smoke.