We conducted this study to determine the factors associated with childhood obesity. The subjects were 170 preschool children in Busan. Data were collected by using questionnaires which asked for information about socioeconomic status, parental perception of their child’s weight status and dietary/physical activity behavior. BMI was calculated for each child and their classification was determined, according to their age and sex, as follows: “overweight” at or above the 85th percentile, “normal” for the 15th-85th percentile, and with a BMI below the 15th percentile the children were deemed as underweight. Classification according to BMI percentile showed that 23.5% (18.25±1.33 kg/m2) of the children were overweight, 62.9% (15.51±0.76 kg/m2) normal, and 13.5% (13.23±2.86 kg/m2) were underweight. Socioeconomic status, as represented by the parents' level of education, the occupation of the father and the household income, did not affect the results. However, mothers working outside the household was a factor that was more likely to affect the weight status (p<0.05). Among mothers whose children were overweight, 30% underestimated their children’s weight status (believing them to be of normal weight when they were overweight), and 25% failed to recognize the necessity of weight control for their overweight children. While sedentary activity and total daily activity levels were not related to BMI, the level of physically active leisure activity was inversely correlated with BMI (p<0.05). Although there were no differences in total energy intake, dietary behavior was significantly related to weight status. Overweight children had poor eating tendancies: they eat faster (in less than 15 minutes), overeat, and eat late at night. Based on our findings where hereby recommended the following interventions to help limit weight problems in Korean pre-schoolers: early promotion of active leisure behavior and healthy eating habits, along with attempting to correct parental misperception of healthy weight status for children.