The aim of the present study was to assess the effects of skipping breakfast on diet quality and metabolic disease risk factors in healthy Korean adults. Subjects included 415 employees (118 men, 297 women; 30-50 years old) of Jaesang Hospital in Korea and their acquaintances. Data collected from each subject included anthropometric measurements, 3-day dietary intake, blood pressure, and blood analyses. The subjects were classified into three groups based on the number of days they skipped breakfast: 'Regular breakfast eater', 'Often breakfast eater', or 'Rare breakfast eater'. Participants in the 'Rare breakfast eater' group consumed less rice, potatoes, kimchi, vegetables, fish and shellfish, milk and dairy products, and sweets than did participants in the other two groups (P for trend < 0.05) and ate more cookies, cakes, and meat for dinner (P for trend < 0.05). Participants in the 'Rare breakfast eater' group consumed less daily energy, fat, dietary fiber, calcium, and potassium than did participants in the other groups (P for trend < 0.05). The percent energy from carbohydrates was lower and fat intake was higher in the 'Rare breakfast eater' group than in the other groups (P for trend < 0.01). When diets were compared using the Acceptable Macronutrient Distribution Range for Koreans, 59.1% of subjects in the 'Rare breakfast eater' group consumed more energy from fat compared with the other two groups (P < 0.005). According to the Estimated Average Requirements for Koreans, intake of selected nutrients was lower in the 'Rare breakfast eater' group than in the other two groups (P < 0.05). The risk of elevated serum triglycerides was decreased in the 'Rare breakfast eater' group (OR, 0.3 [0.1-1.0], P for trend = 0.0232). We conclude that eating breakfast regularly enhances diet quality, but may increase the risk of elevated serum triglycerides.