The best indicator of the attractiveness of organic agricultural production is the positive trend on the side of production as well as on sales side. However, to understand whay is organic food market developing rapidly, it is necessary to investigate consumer buying behaviour or motives triggering the purchase of these products. The motives driving organic food buying behaviour can be classified into two groups: egoistic and altruistic (Vega-Zamora et al., 2013). The purchases motivated by egoistic motives can be better understood through studies in which theory of planned behaviour is applied, the theory belonging to racional choice theories (Ajzen, 1991; according to Bamber and Möser, 2007). For understanding of buying behaviour which is altruistic motivated, norm activation theory can be applied (Schwartz, 1977; according to Bamber and Möser, 2007), which is belonging to group of moral theories (Turaga et al., 2010). The purpose of this research is to determine which of two theories, theory of planned behaviour or norm activation theory predicts better buying behaviour of organic food consumers. The model of the theory of planned behavior proposed by Ajzen (1991) was used for the purpose of this research. According to this model predictors of behavioural intention are: attitude, subjective norm (social norm) and perceived behavior control. Besides behavioural intention, direct predictor of behaviour is also perceived behaviour control. The model of the norm activation theory used by Klöckner and Ohms (2009) was used for the purpose of this research. According to this model central variable – personal norm is predicted by social norm, awareness of need, awareness of consequences and perceived behavior control. Besides personal norm, direct predictors of behaviour are also social norm and perceived behaviour control. Based on a content deliberation next hypothesis is established: Theory of planned behaviour predicts better organic food consumer behaviour than norm activation theory. The chapter Overview of previous research starts with an explanation what consumer behaviour is. It follows describing and classifaying consumer behaviour models, as well as models for understanding of pro-environmental behaviour. Also an overview of researches on organic food consumer behaviour and factors influencing that behaviour is given. The chapter ends with an overview of previous applications of theory of planned behaviour and norm activation theory, and comparison of these theories in predicting different types of behaviour. Since consumer behaviour is complex process, different models are used to help to understand this behaviour. Organic food buying behaviour is considered as proenvironmental behaviour (Steg et al., 2014). The theories for explaining pro-environmental behaviour can be structured by three groups of factors examining: intrapersonal, motivational and interpersonal factors (McDonald, 2014). Taking in consideration internal factors and their influence on pro-environmental behaviour, theories can be categorized into three domains: moral, rational choice and non-rational choice (Jackson, 2005; Turaga et al., 2010; according to McDonald, 2014). Moral theories focus on environmental values as the main driver of pro-environmental behaviour (Jackson, 2005; Turaga et al., 2010; De Groot and Steg, 2010; Binney and Hall, 2011; De Groot and Steg, 2009; Hansla, 2011; Poortinga et al., 2012; Steg et al., 2011; according to McDonald, 2014), whilst rational choice theories focus on the impact of attitudes (McDonald, 2014). The chapter Materials and methods covers research phases from product choice to testing the models. Organic vegetables is selected because it is one of the most often bought organic food categories in the world. After that questionnaire was created and tested on a sample of 30 organic vegetables consumers. Because questions were clear to the respondents, there was not need for corections and the main survey followed. The sample consisted of 404 respondents who bought organic vegetables. Colected data were analyzed in SPSS. Univariate data analysis in terms of frequency and data distribution was conducted first. Than, data measuring constructs of models used in the research were prepared for structural equation modeling. Using AMOS, structural equation modeling was conducted to test models. Models were compared using three parameters: squared multiple correlation, comparative fit index and relative chi square. Higher values of squared multiple correlation and comparative fit index mean better model, as well as lower values of relative chi square. The chapter research results contains descriptive results as well as results of theoris which are tested and compared. The survey results have shown that most consumers (23.5%) claim to buy organic vegetables four times a month, and most often in specialized organic food stores. Three most often bought organic vegetables species are: green salad, tomatoes and carrots. The highest percentage of respondents (48.5%) claim to have moderate knowledge about organic vegetables. Consumers have positive attitude about purchasing organic vegetables, a high degree of perceived behavioral control, and high level of intention to purchase organic vegetables. Degree of social norm in context of organic vegetables buying was medium. Consumers have high degree of awareness of need and moderate to strong degree of awareness of consequences . Consumers personal norm in the context of organic vegetables buying is also high. At the level of theory of planned behaviour significant influence on buying intention of organic vegetables have: attitude and perceived behaviour control. The influence of attitude is stronger than influence of perceived behaviour control. These two variables explain 76% of variance of the intention to buy organic vegetables. Intention to buy organic vegetables has significant positive influence on buying frequency of organic vegetables, explaining 25% of behavioral variance. Perceived behavior control has no significant direct influence on buying behaviour of organic vegetables consumers. At the level of norm activation theory significant influence on central variable – personal norm have: awareness of need and perceived behaviour control. The influence of perceived behaviour control is stronger than inluence of awareness of need. These two variables explain 72% of variance of personal norm in the context of organic vegetables buying behaviour. Other variables: social norm and awareness of consequences have not significant influence on personal norm. Significant influence on buying frequency of organic vegetables, at level of norm activation theory, has only perceived behaviour control explaining 22% of behavioral variance. Personal norm and social norm influence buying behavior of organic vegetables consumers not significantly. Research results show that all three parameters used for comparison of the theories go in favor of theory of plannned behaviour. Namely, theory of planned behaviour explains 25% of behavioral variance and norm activation theory 22%. Comparative fit index for theory of planned behaviour amounts 0.987 and for norm activation theory this index amounts 0.961. Relative chi square for theory of planned behaviour amounts 2.260, and for norm activation theory 3.410. So research hypothesis claiming: Theory of planned behaviour predicts better consumer behaviour of organic vegetables than norm activation theory, is confirmed. The chapter Discussion focuses on the comparison of obtained results in this research and results obtained in previous researches. Also this chapter contains subchapters: the marketing implications as well as research limitations and recommendations for future research. Models used in this dissertation explained a solid percentage of the variance comparing to models used in previous studies on different types of behaviour. Recommendations for business practice are given in the context of both theories. The recommendation is to strengthen attitude toward organic vegetables, perceived behavior control and buying frequency. More positive attitude and higher degree of perceived behaviour control should lead to stronger buying intention and consequently more frequent buying of organic vegetables. Stronger buying intention should lead directly to more frequent buying of organic vegetables. Ads with strong message stressing benefits of consuming pesticides free vegetables would strengthen attitude about how organic vegetables buying smart choice is. Different promotional tools could be used for the strengthening of three important segments of perceived behavior control: perceived market availability of organic vegetables, perceived the closeness of the ogranic vegetables sales point, and perceived price eligibility of organic vegetables. Also different promotional tools could be used for the strengthening of level of awareness of need. Higher degree of awareness of need would result in stronger personal norm, and consequently in more a more frequent purchase of organic vegetables. Since convenience sample was used firm conclusion about organic vegetables buying frequency can not be made. So in future research sample procedure which can provide more concrete conclusion should be used. One of the research limitation is self-reported buying frequency. One item measuring perceived behaviour control at the level of the theory of planned behaviour is also limitation in a certain way. So future reserach should ensure more items measuring constructs of theories used in research. The chapter Conclusion contains a main conclusion of this research, namely that the theory of planned behaviour explains better buying behaviour of organic food consumers, than the norm activation theory. Also recommendations for marketing practice are given.