This paper examines a methodological controversy and aims to show the advantages of introducing an alternative methodological approach, i.e. the 'scientific realist approach', into evaluation studies on health education programmes for smoking cessation. The methodological difficulties of the existing standard evaluation model, i.e. the quasi-experimental approach, are examined. This model fails to investigate how the programme setting influences outcomes (context problem) and draws attention away from understanding why programmes work because it adopts a 'successionist' logic (causation problem). An alternative methodology, the scientific realist approach, is proposed in order to cope with such problems. This approach adopts the 'generative' logic which looks at the matter of causation internally. This logic posits that the working of underlying mechanisms within a more basic level of reality causes relationships between visible events. According to the scientific realist approach, the actual outcomes of smoking cessation programmes follow from the workings of potential mechanisms whose functioning is afforded by contexts conducive to their operation.