OBJECTIVE: To define and explore the sociocultural factors that could enhance (facilitators) or interfere with (barriers) the adequate consumption of a nutritional supplement (NS) by children from 6 to 59 months of age, provided as part of the national program Oportunidades. MATERIAL AND METHODS: Qualitative study in rural communities of Chiapas and Veracruz. Forty-four semi-structured interviews and 25 focus groups were conducted with mothers and other key informants. The framework analysis approach was used. RESULTS: Facilitators. The NS is free, is highly accessible, is positively accepted and mothers believe the physicians recommendations. Barriers. Lack of adequate storage and distribution, poverty conditions, intrahousehold dilution (within the family members), beliefs regarding child feeding and the purpose of the NS. CONCLUSION: Results shows the incongruence between the Programs recommendations and the preferences and practices of the target population and provides important elements to be considered in the promotion of the NS .