Objective: To evaluate a school-based stop smoking pilot project and to understand the teenage experience of smoking and quitting within that context. Design: Flexible design methods. Setting: A Kent (United Kingdom [UK]) secondary school. Methods: Semi-structured interviews analyzed following a grounded theory approach. Results: The main themes that emerged were ambivalence and fluidity. Young people can have mixed feelings towards their smoking behaviour. They experience ambivalence at the societal level in the messages they get about starting and stopping smoking and at the individual level in how they feel about other people smoking. Ambivalence in the quitting process is intensified by the phenomenon of addiction. Fluidity characterizes their way of life; things are not fixed and arrangements open to change. This was reflected in the way they approached coming to appointments. Conclusion: This research contributes a new perspective on the teenage smoking and quitting experience which others working in the field may find useful in characterizing their experience of working with young people. This ambivalence and fluidity suggests that a flexible approach in interventions with young people may be a key to success. (Contains 2 tables.)