The objective of this paper is to analyse consumers’ attitudes and acceptability of GM food products in Spain. From the methodological point of view, a three-equation model of consumer behaviour is estimated assuming a kind of causal chain among the degree of knowledge, attitudes and buying intentions. Explanatory variables include socioeconomic characteristics of respondents as well as endogenous variables of the previous equations. The model provides a better knowledge of how attitudes and buying intentions towards GM food are formed. Higher educated consumers, more concerned about labelling information and less about price, and regular buyers of organic foods show a higher (not necessarily better) knowledge on GM technology and its consequences. However, those consumers with a lower level of knowledge, together with those who are not concerned about safety, are not used to recycle but to purchase fast food generate more positive attitudes towards GMs, which finally determine future purchasing intention.