The present study investigated the role of socio-demographic and lifestyle determinants on the nutrition knowledge of Belgian women and the association between their knowledge and dietary behaviour. A total of 803 women, aged 18-39 years, were included in a cross-sectional study and completed a general and nutrition knowledge questionnaire and a 2-day food record. Their height and weight were measured under standardised conditions. Linear regression models showed independent significant associations between the following determinants and the women's nutrition knowledge (in order of importance): educational level, age, kind of occupation, smoking behaviour, and work status. Inconsistent or no associations were found for body mass index, physical activity, living situation, and whether or not they had children. The investigated determinants accounted for 13-14.5% of variance in total nutrition knowledge. A rise in nutrition knowledge was associated with a significant rise in consumption of vegetables and fruit, but no differences were seen for other dietary indicators. Most important determinants of the women's nutrition knowledge were educational level, age and their kind of occupation. Women who had better knowledge of nutrition also exhibited better dietary behaviour, thus underlying the importance of nutrition education for improving dietary behaviour.