The present research aimed to develop the implicit relational assessment procedure (IRAP) as a means of quantifying tobacco addiction in terms of implicit (i.e. automatic) evaluative processes. Chapter 1 begins by highlighting the fundamental importance of such processes to the losses of personal autonomy which characterise tobacco addiction. Accordingly, thereafter, Chapters 1-3 involve critically reviewing all major measures of addiction-related implicit processes in terms of their respective abilities to distinguish between implicit evaluating of one topic as distinct from another. The review culminates by recommending the IRAP, and its behaviour analytic rationale, as a tool for both functional and cognitive theorizing about tobacco addiction. Chapter 4 reports a study showing that the IRAP compares favourably with the most popular implicit measurement tool, the implicit association test (IAT), in terms of its ability to validate against multiple defining features of tobacco addiction. Indeed, this was despite the fact that both implicit measures were focused on evaluative topics specifically designed to favour the IAT rather than the IRAP; and also despite the fact that as a result the relevant IAT convincingly outperformed all of its predecessors in the literature. In response, Chapter 5 describes research that explored the potential of the IRAP to target complex, mood-conditional aspects of smokers’ implicit reasons for smoking that were unavailable to the IAT, or any other implicit measure. Crucially, by revealing motivational distinctions that were simply not available using other existing measures of implicit cognition, the IRAP’s experimental precision allowed us to identify aspects of implicit evaluating with unprecedented levels of criterion validity in relation to tobacco addiction. For example, these findings suggested a preliminary functional model wherein tobacco addiction is motivated by complex, coordinated and mood-dependent networks of implicit evaluative processes which collectively insist that one should regulate one’s ongoing emotional experiences – particularly negative craving-related affect – by smoking. Extending this model, the three experimental studies reported in Chapters 6 and 7 confirmed that smokers’ most popular, and also least successful, method of managing their (implicit) tobacco cravings is ultimately selfdefeating insofar as it involves experientially avoidant tactics like thought suppression. Accordingly, Chapter 8 concludes by recommending the IRAP, with certain important qualifications, as a useful means of quantifying tobacco addiction in such a way as to begin clarifying the motivational problem(s) that smoking-cessation treatments must ultimately tackle.