Two chemical isomers of 3-nitrobenzotrifluoride, namely 1-(4-chlorophenylsulfanyl)-2-nitro-4-(trifluoromethyl)benzene, C(13)H(7)ClF(3)NO(2)S, (I), and 1-(4-chlorophenylsulfanyl)-4-nitro-2-(trifluoromethyl)benzene, C(13)H(7)ClF(3)NO(2)S, (II), have been prepared and their crystal structures determined with the specific purpose of forming a cocrystal of the two. The two compounds display a similar conformation, with dihedral angles between the benzene rings of 83.1 (1) and 76.2 (1) degrees, respectively, but (I) packs in P-1 while (II) packs in P2(1)/c, with C-H.O interactions. No cocrystal could be formed, and it is suggested that the C-H.O associations in (II) prevent intermolecular mixing and promote phase separation.