The objective of this thesis is to engage in the optimization of waste separation behaviour. To reach this objective, major drivers which influence said behaviour were identified. In the first step a literature research was executed to find drivers which were already discussed in former studies. These drivers were divided into two groups: the non-demographic drivers and the demographic drivers. In this form they were then presented to a group consisting of experts in waste management, sustainability and sociology and behaviour studies, as well as to a population of Barcelona and one of Leoben. These groups were asked to rank these drivers according to their importance. The obtained rankings were then processed for each group separately via pairwise comparison matrices to obtain weightages. The results of the different groups were discussed, compared and the differences interpreted. They show that the most important non-demographic drivers are internal drivers like ¿Beliefs and values¿, ¿Habits¿ and ¿Environmental concern¿. The only really important external driver is ¿Convenience of the collection system¿. It was also found that the perceptions of the three questioned groups about the non-demographic drivers are very similar. One of the most important demographic drivers is ¿Level of education¿ which seems to be perceived to be related to knowledge and understanding about environmental issues and the recycling process. Also very important is the driver ¿Location¿ which is connected to the type if collection system and therefore, also to the convenience a person experiences during waste separation. It was found that the results for the demographic drivers show greater diversity between the groups than the results for the non-demographic drivers. The comparison of the importance of non-demographic and demographic drivers show, that all groups perceive the non-demographic drivers to have a bigger influence.