Much progress has been made in the field of tobacco control but the fact that the smoking prevalence in most Western countries is declining only slowly and still rising in many non-Western countries underlines the need to develop new ways to increase smoking cessation rates. Smoking-related biomarkers - biochemical, physiological or anatomical indices of exposure, risk and harm linked to smoke constituents - have been instrumental in furthering tobacco control, and this thesis examines the role of these biomarkers in smoking cessation. Study 1 evaluated whether biomarkers of exposure can be substituted by self-report and found that most smokers have only limited awareness regarding their level of exposure. Study 2 qualitatively explored smoking cessation in smokers and ex-smokers and examined their views on existing interventions in the NHS as well as on novel interventions involving biomarker feedback. Most participants commented positively on the Stop Smoking Services and welcomed the use of biomarkers in smoking cessation interventions. Study 3 tested the effectiveness of such an intervention adding feedback of an exposure and risk biomarker to brief advice in a randomised controlled trial. The intervention successfully altered cognitive antecedents of behaviour change but increased cessation rates only among smokers with high self-efficacy levels in comparison with the control group. Studies 4 and 5 used exposure and harm biomarkers from a nationally representative sample to determine smoking rates among people with objective signs of chronic obstructive pulmonary (COPD) or cardiovascular (CVD) diseases and to evaluate the potential impact of a diagnosis on smoking cessation. People with COPD but not CVD were more likely to smoke a disease diagnosis was associated with higher motivation to stop among smokers with COPD and with higher cessation rates in smokers with a CVD. The importance of these findings for the measurement of smoke intake, improvement of interventions and detection and treatment of smokers with diseases is discussed
