The present study discloses the influence of aliphatic (cyclohexane) and aromatic solvents with different pi-electron densities viz. toluene, o-xylene, ethylbenzene (EB), and p-diethylbenzene (PDEB) on the cobalt-catalyzed high cis-polymerization of 1,3-butadiene. Comparative study in cyclohexane and toluene has been conducted in view to understand the effect of solvent on catalyst reactivity, molecular weight of the polymer, and polymerization kinetics. At given reaction conditions conversion is highest (68%) in cyclohexane, followed by toluene (27%) and EB (8%). Respective polymerization rate constants are found to be 0.0170, 0.0020, and 0.0008 min(-1). Higher viscosity average molecular weight (M) of polymer observed in toluene (M = 4.68 x 105) compared to that in cyclohexane (M = 2.37 x 105) indicates that the presence of lower number of active sites leads to higher molecular weight. Cyclohexane shows activity at a lower water:alkylaluminum ratio than does toluene; as the pi-electron of toluene reduces the Lewis acidity of hydrolyzed diethylaluminum chloride (DEAC) more than cyclohexane, where influence of pi-electron is absent. The effect of different solvents has also been demonstrated by respective shifting of wavelength (A) of solvent pi ->pi*, cobalt (4)A(2) -> T-4(1)(P), as well as T-4(1) (g) (F) -> T-4(1) (g) (P) and activated butadienyl pi(HOMO) -> pi*(LUMO) transitions.