Chapter 1 provides an introduction to the context in which four studies were conducted to assess how exercise impacts on nicotine addiction processes. Chapter two gives an overview of some contemporary theories of addiction and the possible processes underlying addiction. The second part provides details of chronic (intervention) and acute studies that have assessed the effects of exercise on cigarette cravings, smoking withdrawal symptoms and cue-reactivity. The findings will be discussed in terms of the type and duration of exercise utilised and the strength and duration of effects on subjective desire to smoke and cigarette cravings. Lastly, some possible mechanisms by which exercise may exert effect on cravings and cue-reactivity are identified. This background provides a basis for the subsequent studies. Chapter three describes an experimental study (Study 1), in which fMRI was used to compare brain activation response to smoking-related stimuli (compared with neutral stimuli) during nicotine abstinence and immediately following smoking a cigarette. The aim of this study was to pilot methods for future fMRI studies to assess the effects of a single session of exercise on brain responses to smoking-related images. Previous evidence has shown that during periods of deprivation, stimuli of perceived ‘salient’ importance (i.e. smoking-related images, such as images of people smoking) are associated with enhanced activation in areas of the brain known as the mesocortical-limbic circuit (i.e. nucleus accumbens, amygdala, hippocampus, prefrontal cortex, orbitofrontal cortex and anterior cingulate) (Due et al, 2002; David et al 2005; McClernon et al, 2005; Smolka et al 2006). Chapter four and five describe two further fMRI studies (Study 2 and 3). These two studies sought to investigate the effects of an acute bout of exercise on regional brain activation to smoking-related (compared to neutral) images. The first study (Chapter 4) uses an event-related design whereby smoking and neutral images were randomly presented during scanning. The second study (Chapter 5) employs a block design method, whereby individuals view a randomised block of either 3 smoking or 3 neutral images. Chapter six describes a study (Study 4) designed to examine the effects of an acute bout of exercise on attentional bias to smoking-related images. This study utilised an eye tracking methodology to compare duration of gaze and direction of fixation following a session of passive rest or acute exercise. Previous studies in this area (without the exercise session comparison) have demonstrated that’s smokers show enhanced gaze duration toward smoking stimuli (versus control cues or non smokers) (i.e. Mogg et al, 2005) and during nicotine deprivation (i.e. Field et al, 2004). Some studies have suggested these biases in attention may be associated with higher subjective cravings (i.e. Mogg et al, 2005; Field et al, 2009). All studies assessed the effects of exercise on subjective cravings to smoke. An overall summary of findings and discussion is presented in Chapter 8. The findings are conceptualised and integrated into existing theories of addiction, and ideas for future research are presented. The work presented in this thesis has been presented at both National and International conferences and is either published or is under review in peer review journals. Please see the footnotes at the start of each chapter for more details.