Objectives: In general populations, the adverse effects of smoking on coronary risk have been demonstrated to be greater in women than in men; whether this is true for individuals with diabetes is unclear. Design: Cohort study. Setting: 20 countries worldwide participating in the ADVANCE (Action in Diabetes and Vascular Disease: Preterax and Diamicron modified release Controlled Evaluation) trial. Participants: 11 140 patients with type 2 diabetes aged ≥55 years and in cardiovascular risk at the time of randomisation. Primary and secondary outcome measures: Major cardiovascular events (death from cardiovascular disease, non-fatal stroke or non-fatal myocardial infarction (MI)), all cardiovascular events (major cardiovascular event or peripheral arterial disease or transient ischaemic attack), and all-cause mortality. Secondary outcome measures were major coronary events (fatal and non-fatal MI), major cerebrovascular events (fatal and non-fatal stroke), nephropathy (new or worsening renal disease), and all cancer. Results: At baseline, 6466 (56% women) participants were never-smokers, 1550 (28% women) were daily smokers and 3124 (21% women) were former smokers. Median follow-up time was 5 years. In Cox regression models after multiple adjustments, compared with never smoking, daily smoking was associated with increased risk of all primary and secondary outcomes with the exception of major cerebrovascular disease. Only for major coronary events was there any evidence of a stronger effect in women than in men (ratio of the adjusted HRs women:men; 1.64 (0.83 to 3.26) p=0.08).