Objective: The aim of this study is to examine the prevalence and risk factors of periodontitis. Methods: The total of 4,477 adults (3,860 adults without DM (non-DM group) and 617 adults with DM (DM group)) over 30 years old was evaluated. The data was from Korean National Health and Nutritional Examination Survey in 2012. Using multiple logistic regression, we estimated odds ratio [OR (95% confidence limit)] for independent risk factors for periodontitis. Results: The mean age was 49.8 years old, BMI 24 and number of teeth 24.9. The prevalence of periodontitis in DM group was 30 ± 1.2% and 25 ± 1.2% of non-DM group. In non-DM group, associated factors for periodontitis were age, male, low education, low income, and rural habitation ( P < 0.05). In DM group, associated factors were male and low education ( P < 0.05). In non-DM group, associated factors for periodontitis were age [1.035 (1.025, 1.046)], male [1.644 (1.269, 2.131)], urban habitation [1.737 (1.229, 2.455)], WC [1.014 (1.001, 1.028)], smoking [1.583 (1.215, 2.062)], and oral pain [1.486 (1.186, 1.861)], and tooth brushing frequency was inversely associated [0.777 (0.671, 0.899)]. In DM group, risk factors were smoking [1.939 (1.003, 3.751)] and oral pain [2.383 (1.4600, 3.888)]. Using oral hygiene product was inversely associated [0.505 (0.309, 0.826)]. Conclusion: Smoking is associated with periodontitis regardless of DM. Tooth brushing is inversely associated with periodontitis in adults without DM. Using oral hygiene product is inversely associated with periodontitis in adults with DM. In addition to tooth brushing and non-smoking, ‘oral hygiene product’ can reduce periodontal disease in adults with DM.