Geometrical structure, electronic and optical properties, electronic absorption spectra, vibrational frequencies, natural charge distribution, thermodynamic properties, and MEP analysis of trans- and cis-structures of Flupentixol have been investigated using DFT and TDDFT methods with the B3LYP hybrid functional and 6-311+G** basis set. The results of calculation of the quantum properties verify the greater activity of the cisstructure of this drug.