The interaction of sulfur dioxide (SO2) and sulfur trioxide (SO3) has been studied with terthiophene (as a model of polythiophene, denoted as 3PT) using density functional theory (DFT) at B3LYP/6-31+G (d) level of theory and the results were compared to the non-DFT at M06-2X/6-31+G (d) level of theory. Quantum chemical analysis has been done to study on frontier molecular orbitals assuming that, the orbital energy of 3PT changes upon interaction with SO2 and SO3. The interaction energies of SO2 and SO3 on 3PT at optimized configurations achieved -10.4 and -22.6 kJ mol−1 respectively.