With the introduction of the mandatory EU organic logo for all organic food products in 2010 the European Commission aimed at supporting a sustainable development and the effective functioning of the internal market for organic food. This approach presupposes consumers’ knowledge of the logo and their understanding of its meaning. By means of an online survey with 3000 participants in 6 European countries, knowledge of the logo and attitudes towards organic farming and European labelling as well as organic food purchase behaviour and socio-demographic indicators were elicited. The results indicate that knowledge of the logo is low. Only about 15% of all respondents knew its meaning. A binary logistic regression revealed that knowledge of the logo is higher among consumers who regularly buy organic food, who have good knowledge on the principles of organic farming and who consider freedom of chemical residues, of synthetic additives and organic production as important features of a high quality product. High education has a positive impact on the awareness of the logo, while age has a negative one. Large differences in knowledge exist between countries: the probability to know the EU logo is highest in Estonia and in Poland. Generally, knowledge of the EU organic logo is such low that the achievement of its purpose is doubted. Reasons are supposed to be the limited self-explanatory content of the logo as well as lacking awareness, resp. promotion campaigns.