Results of case studies describing people's different intuitive risk perceptions of various exposure sources from telecommunication technologies in Serbia and in Montenegro are presented. Furthermore the cognitive link between risk perception and exposure perception of radio frequency electromagnetic fields is analysed. The knowledge about possible exposure features is evaluated and tested in a regression analysis to investigate the impact on lay people's estimation of the dangerousness of several exposure situations. The results show that participants are more concerned about base stations than about all other RF EMF sources. Moreover, it seems that the knowledge about exposure characteristics is source specific. All in all the results raise doubts whether the knowledge about exposure features plays a crucial role in EMF risk perception.