Ground state geometries of a series of 1, 8-naphthalimide derivatives were calculated by density functional theory (DFT). Their UV-Vis absorption spectra in gaseous, C6H12 (cyclohexane) and CH2Cl2 environments were calculated by the time dependent-DFT (TDDFT) method and the conductor polarizable continuummodel-TDDFT (CPCM-TDDFT) method. We found that theoretical values were in od agreement with X-ray geometric parameters. The addition of various substituents (H, methyl, phenyl, and naphthyl) to the 4 and 5 positions of the naphthalic ring's amines lengthened the (N—C) bond length between the amine and the naphthalimide moiety. This bond lengthening resulted in more intramolecular charge transfer and a lower energy gap. Both the bathochromic effect and the frontier orbital electron cloud density showed that the absorption maximum corresponds to a π-π* transition. By comparison to the maximumabsorption peak of UV-Vis absorption spectrumof the B isomer, that of the A isomer was red shifted and this was mainly attributed to more intramolecular charge transfer and a lower energy gap.