The interactions between molecules and substrates play an important role in the growth of organic thin films. The metallic and semimetallic substrates, owing to the different electronic structures, would have distinct interactions with molecular films. Here we made a comparative studies on the 2D self-assemblies of DCA molecules on the metallic Cd(0001) and semimetallic Bi(111) surfaces. It was found that, on the Cd(0001) surface, the DCA thin films grown at low temperature exhibit a 3D growth mode, where the monolayer islands, two-layer islands, and three-layer islands coexist on the Cd(0001) surface. When deposited at room temperature, the DCA molecules exhibit a 2D growth mode, where the monolayer DCA adopt the 4×Ö13 reconstruction with respective Cd(0001). The commensurate epitaxy indicates that there is strong interaction between DCA molecules and Cd(0001). In clear contrast, the DCA molecules deposited on the semimetallic Bi(111) surface at low temperature exhibit a 2D growth mode. Furthermore, a Moiré pattern with the periodicity of 2.6 nm has been observed in the DCA monolayer, indicating the incommensurate epitaxy of DCA monolayer on Bi(111). This can be explained by the weak interaction between DCA and Bi(111) substrate. These results demonstrate that both of the electronic structure of substrates and substrate temperatures can be used to mediate the structures of morphology of DCA films.