Im, Chegyong. 2012. Double Subject Constructions in Korean: A Purely Derivational 3D Merge Approach. Linguistic Research 29(1), 197-215. In this paper, we try to provide theoretical evidences for the structure of DSCs suggested in Im (2002) and Tm (2009), adopting and adapting the derivational approaches including Starke (2001) and Suranyi (2006). We argue against the multiple agree approach and movement approach outlining their theoretical and empirical problems. Then, we will show that the Natural Relation suggested in (lrohmann (2003) and the purely derivational approach in Suranyi (2006) support my argument that NP2 is the subject of the constructions and that the sequence of functional projections (FSeq) suggested in Starke (2001) resolves the concatenation of the constructions, The most advantageous thing is that Merge of NPT as Topic/Focus can be explained in 3D Merge hypothesis suggested in Boeckx (2008), and In (2002, 2004, 2005a, 2005b, 2006a, 2006b, 2007, 2008, 2009, 2010, 2011).