BACKGROUND: Perception of body size is a key factor driving health behavior. Mothers directly influence children's nutritional and exercise behaviors. Mothers of ethnic minority groups and lower socioeconomic status are less likely to correctly identify young children as overweight or obese. Little evaluation has been done of the inverse-the child's perception of the mother's weight. OBJECTIVE: To determine awareness of weight status among mother-child dyads (n=506). DESIGN: Cross-sectional study conducted in an outpatient pediatric dental clinic of Columbia University Medical Center, New York, NY. PARTICIPANTS: Primarily Hispanic (82.2 %) mothers (n= 253), 38.8±7.5 years of age, and children (n=253), 10.5± 1.4 years of age, responding to a questionnaire adapted from the validated Behavioral Risk Factor Surveillance System. MAIN MEASURES: Anthropometric measures-including height, weight, and waist circumference-and awareness of self-size and size of other generation were obtained. KEY RESULTS: 71.4 % of obese adults and 35.1 % of overweight adults underestimated size, vs. 8.6 % of normal-weight (NW) adults (both p < 0.001). Among overweight and obese children, 86.3 % and 62.3 % underestimated their size, vs. 14.9 % NW children (both p<0.001). Among mothers with overweight children, 80.0 % underestimated their child's weight, vs. 7.1 % of mothers with NW children (p<0.001); 23.1 % of mothers with obese children also underestimated their child's weight (p < 0.01). Among children with obese mothers, only 13.0 % correctly classified the adult's size, vs. 76.5 % with NW mothers (p<0.001). Among obese mothers, 20.8 % classified overweight body size as ideal, vs. 1.2 % among NW mothers (p<0.001). CONCLUSION: Overweight/obese adults and children frequently underestimate their size. Adults misjudge overweight/obese children as being of normal weight, and children of obese mothers often underestimate the adult's size. Failure to recognize overweight/obesity status among adults and children can lead to prolonged exposure to obesity-related comorbidities.