The co-existence of under-and overnutrition in developing countries might be the resultant factor of a marked shift in dietary and lifestyle practices of people, especially in urban areas. The eating of high fat, high caloric diets, the presence of inactive entertainment devices and mechanized labour influence patterns of food demand and physical activity. This study identified factors associated with the occurrence of under/overweight or normal/normal nutritional status of child-mother pairs in one household. This study was conducted in two phases. The first phase was a survey of 376 child-mother pairs. The children aged 33-83 months were attending classes in government day care centres. Anthropometric indices: weight-for-age Z score (WAZ) < or = -2SD was used to classify underweight in children. WAZ+1 to -1SD was used to indicate normal nutritional status in children, specifically for this study, in order to establish a more homogenous group. Body mass index (BMI) > or = 25 kg/m2 was used to measure overweight among mothers. Results showed that about 59% of the child-mother pairs were suffering from two different types of malnutrition. From this, 31 (8.2%) child-mother pairs in the same household were experiencing underweight/overweight: the child was underweight and the mother was overweight. The second phase of the study was an in-depth study of these 31 under/overweight child-mother pairs and 30 randomly selected normal/normal pairs. Pre-tested questionnaires were used to gather socio-economic-demographic data; 3 day 24-h food recall for dietary intake and 24-h activity recall for physical activity. Results showed that the different factors associated with the existence of underweight child/overweight mother (UC/OM) or normal child/normal mother (NC/NM) in this study were: mother's educational level, mother's occupation, and number of children in the household; energy intake, the preference of meats, sweets and sugars among children or meats and fried foods among mothers; and mother's perception on body size. Physical activity of both mothers and children was higher in the UC/OM than in the NC/NM group. The problem of undernutrition and overnutrition in one household poses enormous challenges. Although this study cannot make an inference to the whole population, the results indicate that there is a need to consider whether public health programs should focus on healthy diet and lifestyle patterns that will lead to optimal health outcomes at both ends of the spectrum of nutritional status.