BACKGROUND: Many foods are associated with chronic obstructive pulmonary disease (COPD) symptoms or lung function. Because foods are consumed together and nutrients may interact, dietary patterns are an alternative way of characterising diet. A study was undertaken to assess the relation between dietary patterns and newly diagnosed COPD in men. METHODS: Data were collected from a large prospective cohort of US men (Health Professionals Follow-up Study). Using principal component analysis, two dietary patterns were identified: a prudent pattern (high intake of fruits, vegetables, fish and whole grain products) and a Western pattern (high intake of refined grains, cured and red meats, desserts and French fries). Dietary patterns were categorised into quintiles and Cox proportional hazards models were adjusted for age, smoking, pack-years, (pack-years)(2), race/ethnicity, physician visits, US region, body mass index, physical activity, multivitamin use and energy intake. RESULTS: Between 1986 and 1998, 111 self-reported cases of newly diagnosed COPD were identified among 42,917 men. The prudent pattern was inversely associated with the risk of newly diagnosed COPD (RR for highest vs lowest quintile 0.50 (95% CI 0.25 to 0.98), p for trend = 0.02), and the Western pattern was positively associated with the risk of newly diagnosed COPD (RR for highest vs lowest quintile 4.56 (95% CI 1.95 to 10.69), p for trend <0.001). CONCLUSIONS: In men, a diet rich in fruits, vegetables and fish may reduce the risk of COPD whereas a diet rich in refined grains, cured and red meats, desserts and French fries may increase the risk of COPD.