We review recent results about the macroscopic description of phase separation in the 2D Ising model, with special emphasis on boundary effects and related surface phase transitions. In particular, after having recalled some facts about the wetting transition, we describe two situations in which this transition has major consequences at the macroscopic scale. We also briefly describe a more general situation for which it is possible to derive the thermodynamical variational problem characterizing the interfaces of the equilibrium state.