Previous studies using the theory of planned behaviour (TpB; Ajzen 1991) have shown, based on the aggregation principle, that compound measures increase the explained variance in the context of sustainable behaviour and, thus, argue for the use of aggregated measures (Kaiser et al. 2005). Studies using this approach, however, cannot provide differentiated information on underlying mechanisms of specific sustainable behaviour, which, in turn, might be necessary to develop successful intervention strategies; particularly because previous studies have suggested that consumers’ interest in the dimensions of sustainability (economic, social, and environmental) might differ (Bögel 2015). This study aims to test to heterogeneity of the constructs included in the TpB and, thus, the necessity of specific measures.A survey study with students (n = 142) from a German (n = 65) and a Croatian (n = 77) university was conducted. It examined participants’ attitudes, social norms and perceived level of control towards sustainable fashion consumption. According to the assumptions made above the three variables were measured separately concerning a) the social and b) the environmental dimension. The study lend support towards the assumed heterogeneity: In Germany, attitudes towards the social dimensions of sustainable fashion consumption (M = 4.69, SD = 1.53) were significantly more positive than towards environmental aspects (M = 4.22, SD = 1.75), t(64) = 4.34, p < .001. In contrast, participants from Croatia significantly perceived the environmental aspects (M = 3.51, SD = 1.84) to be more important than the social dimension (M = 3.13, SD = 1.62), t(76) = -2.17, p = .033. In addition, regarding country differences, the study showed that participants from Germany had a significantly more positive attitude towards the social as well as the environmental dimension of fashion consumption than those from Croatia. Similar effects were found for social norms and perceived level of control. The findings on differences between the social and environmental dimensions of sustainability attitudes confirm the assumed heterogeneity of the construct. The differences found between the two countries in this regard support the assumption that the insights gained from a specific measurement approaches are needed for successful interventions strategies, e.g. aimed at increasing sustainable Friday 1st September· 09:00 – 10:30 h. 259fashion consumption in the two countries. The differentiation between the environmental and the social dimensions of sustainability attitudes and sustainable behaviour are a starting point in this regard, but further research is needed.