OBJECTIVE: There are limited data on the risk of pulmonary disease in patients with diabetes. The aim of this study was to evaluate and compare the incidence of asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, pneumonia, and lung cancer in patients with and without a diagnosis of diabetes. RESEARCH DESIGN AND METHODS: We conducted a retrospective, longitudinal cohort study using the electronic records of a large health plan in northern California. Age and sex data were available for all cohort members (n = 1,811,228). Data on confounders were available for a subcohort that responded to surveys (n = 121,886), among whom Cox proportional hazards regression models were fit. RESULTS: Age- and sex-adjusted incidence rates and 95% CIs were calculated for members with and without diabetes in the full cohort and the subcohort. No difference was observed for lung cancer, but the incidence of asthma, COPD, fibrosis, and pneumonia was significantly higher in those members with a diagnosis of diabetes. These differences remained significant in regression models adjusted for age, sex, race/ethnicity, smoking, BMI, education, alcohol consumption, and outpatient visits (asthma hazard ratio [HR] 1.08 [95% CI 1.03-1.12], COPD HR 1.22 [1.15-1.28], pulmonary fibrosis HR 1.54 [1.31-1.81], and pneumonia HR 1.92 [1.84-1.99]). The risk of pneumonia and COPD increased significantly with increasing A1C. CONCLUSIONS: Individuals with diabetes are at increased risk of several pulmonary conditions (asthma, COPD, fibrosis, and pneumonia) but not lung cancer. This increased risk may be a consequence of declining lung function in patients with diabetes.