The staggering growth of online social networking and the potential of Social Networking Sites as marketing channels has become an issue of attention and interest by commercial organizations. This explorative study provides the basis for understanding the nature and behaviour of users of these sites. Based on a national sample, this paper investigates the demographics, profiles and behaviour of participants of Social Networking Sites in The Netherlands. The paper compares the online behaviour of users and non-users of SNS and reveals that the first category of networked citizens is much more active on most types of online activities. Furthermore the study identifies the profile of the average participant in online social networks, identifies preferences and reveals ways that online citizens are engaged with this particular form of social media. The findings provide a better understanding of the importance of the Social Networks for the digital citizen and present useful facts to marketers eager to integrate these media into their marketing approaches and strategies; they also present researchers of human behaviour with interesting insights on the role of the online social networks as platforms of social interaction and communication