The high increase of usage rates of Social Networking Sites (SNS) such as Facebook are a worldwide phenomenon as are people spending hours in Facebook especially among young adolescents. However, beside their useful and enjoyable features, SNS like Facebook have also proven to have undesired outcomes in terms of technostress, social overload, or even addiction. Addiction as a variable in adoption models has been introduced into the IS community by Turel and Serenko (2011) who operationalized online-auction addiction and assessed its impact on adoption determinants as perceived usefulness. By means of an empirical study of 125 young adults, the present research shifts the focus to the causes of addiction using the example of Facebook. We thereby focus on three groups of addiction predispositions (Family dysfunction, peer influence and behavioral conditioning) and empirically investigate their impact on Facebook addiction.