1Khorramabad Branch, Islamic Azad University, Iran
2University of Zagreb,Croatia
3Arak University, Iran
In this paper we present explicit formulas for the eccentric connectivity index of three classes of chain hexagonal cacti. Further, it is shown that the extremal chain hexagonal cacti with respect to the eccentric connectivity index belong to one of the considered types. Some open problems and possible directions of further research are mentioned in the concluding section.