AIMS/HYPOTHESIS: The aim of this study was to assess the associations of lung function with insulin resistance and Type 2 diabetes. METHODS: We did a cross-sectional study of 3911 women who were 60 to 79 years old from 23 British towns, assessing the association of measures of lung function with insulin resistance (based on fasting insulin and glucose concentrations) and Type 2 diabetes (World Health Organisation diagnostic criteria). RESULTS: Forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were inversely associated with insulin resistance and prevalence of Type 2 diabetes. In age-adjusted analyses, the homeostasis model assessment (HOMA) score (insulin resistance) decreased by 5% (95% CI: 2-7%) for a one standard deviation increase in log FEV1 and by 8% (95% CI: 6-10%) for a one standard deviation increase in log FVC. With additional adjustment for height, smoking, BMI, waist-to-hip ratio, physical activity, white cell count, adult social class, childhood social class and respiratory medication, these associations attenuated to 3% (95% CI: 1 to 5%) and 5% (95% CI: 3 to 8%). The fully adjusted odds ratio for diabetes prevalence was 0.85 (95% CI: 0.74-0.98) for a one standard deviation increase in log FEV1 and 0.80 (95% CI: 0.70-0.92) for a one standard deviation increase in log FVC. Forced expiratory flow in the central period of FVC was not associated with insulin resistance or diabetes. CONCLUSIONS/INTERPRETATION: Lung function measures which predominantly reflect lung volume are inversely associated with insulin resistance and Type 2 diabetes. These associations could reflect childhood exposures which affect lung growth and also programme insulin resistance.