Differentiation can be the result of both integration and disintegration processes in the EU. Whereas the prospective post-Brexit relations between the EU and UK constitute a clear case of differentiated disintegration, an alternative model of future EU-Turkey relations is increasingly being discussed in terms of differentiated integration. Thus, building on the existing differentiation literature, the objective of this chapter is to juxtapose and compare various models proposed for future EU-UK relations on the one hand and EU-Turkey relations on the other. The central research question is to what extent could the EU-UK experience of differentiation as a result of disintegration serve as an inspiration for re-construction of EU-Turkey relations beyond accession paradigm and towards differentiation as a result of selective integration. We examine both the range of external differentiation options for EU economic and security relationship with the two countries, as well as the constraints and scope conditions for such a relationship that affect both the UK and Turkey.