Small uncontrolled trials of use of Respiragene in smoking cessation clinics in New Zealand and USA show an improvement in smoking cessation at six months after a Respiragene intervention with quit rates of 30-35%. The trial hypothesis is that smokers who have the Respiragene test and a full explanation of their risk score will have a better quit rate at 4 weeks and at six months (after completion of their eight weekly smoking cessation clinic sessions) than controls. Smoking cessation at the six month follow up will bw confirmed by testing for salivary cotinine. Based on data from Young's small trial, we also hypothesise that this uplift of quit rate will be seen for subjects with both high risk scores and average risk scores (there is no low risk category for smokers). These hypotheses are the basis of the primary end points.