Purpose: to investigate the relationship of between socioeconomic characteristics, and weight perception and lifestyle on body mass index (BMI) in Korea. Method: Participants were 2,405 people recruited from the 2007 Fourth Korea National Health and Nutrition Examination Surveys. Data included weight perception, BMI, and lifestyle factors and was analyzed using ${\chi}$ 2-test, logistic regression Results: Perception of weight was significantly different according to gender, age, education and residence. In the obesity group 21.6% perceived their weight as normal whereas 29.6% of the normal group perceived their weight as obese. In the obesity group, men who were over 70 years old, rural residents and only had elementary education perceived their weight range as normal. In the normal weight group, women who were urban residents and university graduates more frequently perceived their weight as obese. Logistic regression analysis of lifestyle factors, indicated that misperceived obesity was associated with walking (OR=0.703, 95% CI=0.553-0.896), weight control (OR=2.693, 95% CI=2.080-3.485), and health exam (OR=0.730, 95% CI=0.567-0.940) whereas misperceived normal weight was associated with walking (OR=0.696, 95% CI=0.497-0.975), weight control (OR=0.523, 95% CI=0.363-0.749). Conclusion: Results indicate differences in self-perceived weight and life style and provide information that can be used for health promotion program development.