Standard Density Functional Theory calculations for two mesogenic species (phenylbenzoate derivatives with the terminal and lateral -CN group) are performed in order to study the interaction between two molecules of each derivative. Two steps investigations are done: for isolated molecules and for pair of molecules for each of derivatives. Results of calculations (involving geometry optimization), which are carried out for isolated species, indicate the similar geometries (except -CN groups position) although different electronic structures of molecules of both derivatives. Examination of the interaction energy of molecule pairs allows one to get their mutual orientation. It is found that for two parallel molecules with terminal -CN group the interaction energy reaches minimum when they are shifted mutually ca. 0.32 nm. On contrary, for two molecules with lateral -CN group the energy minimum is obtained such a mutual geometry in which atoms of both species can be projected to each other; the molecules do not show tendency to shift. This may serve as indication for existing nematic and smectic A phases, which are observed macroscopically for phenylbenzoate derivatives with terminal and lateral -CN groups, respectively.