This study aims to investigate the social gradient in the reported oral health-related behaviour and oral health status of preschool children. Participants were 1,057 children born between October 2003 and July 2004 in Flanders, Belgium. Oral health examinations were performed by trained dentists when the children were 3 and 5 years old (respectively, in 2007 and 2009); data on dietary habits, oral hygiene habits and dental attendance of the children were obtained through structured questionnaires completed by the parents. Maternal educational level, measured in four categories, was used as a proxy of socio-economic status. Logistic and ordinal regressions showed a social gradient for the oral health-related behaviours: a lower educational level of the mother was related to a higher consumption of sugared drinks between meals and to a lower brushing frequency and dental attendance of the child. Children from low-educated mothers also had seven times more chance to present with caries experience than children from mothers with a bachelor degree. Contrary to the expectations, there was a deviation from the gradient in 3-year-olds from the highest educational group showing an increased risk for caries experience (OR = 3.84, 95 % CI = 1.08-13.65). Conclusion. Already in very young children, a graded relationship is observed between socio-economic position, oral health and related behaviours. The results suggest that different approaches are required to promote oral health during early childhood depending on the mother's educational background. As children from the highest social group also have an increased caries risk, specific techniques may be needed.