Objectives: The aim of this study was to evaluate the association between smoking status and periodontitis risk in Korean adults. Methods: This study used data collected from the 2012 Korea National Health and Nutrition Examination Survey. The final sample included 5,513 subjects over 19 years of age who had completed the necessary health behaviors survey and health examinations. Results: First, based on a stratification analysis by gender, women who smoked more than 20 cigarettes daily had a 9.99-fold greater risk of periodontal disease than men. The risk of periodontal disease was higher in patients who began smoking at a later age. In patients with less than 20-40 lifelong smoking years, there was an increased risk of periodontitis, especially in men. Second, in a stratification analysis based on the presence of diabetes, patients with diabetes and a history of past smoking had a 2.53-fold higher risk of periodontal disease than non-smoking patients with diabetes. In both healthy and diabetic patients, the risk of periodontal disease increased with the daily smoking quantity and with age, and was also increased in individuals with less than 20-40 lifelong smoking years. The risk of periodontal disease was higher in the diabetes group overall, regardless of smoking status. Conclusions: These results suggest that a high level of smoking can increase periodontal disease risk independently of sex and the presence of diabetes in Koreans. This study implies that smoking may be an independent risk factor for periodontal disease.