Commentary on Pardavila-Belio et al. (2015): Reporting on randomized control trials or giving details on how the cake was made-the list of ingredients and the implementation process When reporting on complex behaviour change interventions it is essential to follow published guidance such as that provided by the UK Medical Research Council and journals should require clear descriptions of implementation of the interventions.Evaluating the effectiveness of smoking cessation programmes is a particularly thorny issue, especially when we evaluate multi-component interventions such as that of Pardavila-Belio et al. [1]. The main challenge for evaluations is that many elements, actions and activities are at stake. In the designing process, the intervention has been made up of many interacting components, operating at different levels, with different potential outcomes and mechanisms [2]; in the implementation process important changes from the intended intervention could occur; and at the evaluation point, all these elements should be taken into account to draw sensible conclusions [3]. However, complex interventions have been developed to maximize the likelihood that knowledge generated with the ultimate evidence will obtain the best health outcomes. However, how must we report the evaluation of complex interventions?The Medical Research Council published guidance to assist researchers on how to investigate complex health-care interventions [2,4]. In this guide, randomized controlled trials are regarded as the gold standard for establishing the effectiveness of interventions when randomization is feasible (as in this case). The guide also suggests that the effect of sizes does not make sense without the information on how the intervention was designed (if it were a cake, the ingredients) and implemented (or the way in which the cake was made, including the mixing process, the baking temperature, etc.). Some authors have considered that to grasp the complexity of the implementation we also need to know information about past experience, context, characteristics and profile of clients and practitioners [5].In this paper, authors designed an intervention model based on two major components: (1) existing recommendations made by the US Department of Health and Human Services and (2) a coherent theory that supports the proposed intervention (Theory of Triadic Influence). One might ask that if an intervention is evidence-based, then why conduct further research? Indeed, this is the virtue of the PardavilaBelio et al. study, that gathers several tested interventions and adopts them in a new context (Spain), to be addressed to a specific group of participants (college students) and be delivered by an expert nurse in motivational interviewing and smoking cessation (in brief, la crème de la crème).All these ingredients within the intervention and how they exert the effect can be understood only if we break down the results in several intermediate outcomes and outputs. The sum of their cumulative effect will disclose the 'effecti...