In this chapter the authors discuss the personal scope of the Directive on the Posting of Workers (Dir 96/71/EC) and the implementation thereof in the Member States. The comparative findings are based on two studies conducted by the authors on behalf of the European Commission in 2010/2011. The authors argue that the concepts of ‘posting’ and ‘posted worker’ are crucial for a proper understanding of the scope of application of the Directive and its interaction with the Rome I Regulation on the applicable law to contractual obligations (Reg 593/2008). A clear and enforceable demarcation of the personal scope will help the Member States to combat abuse of the freedom to provide services and to distinguish more clearly between posting and other types of labour mobility. The proposal submitted by the European Commission to that effect (COM (2012) 131) is judged to be an important step in the right direction.