It was shown that the deviation of the product distribution from the Schultz-Flory law upon ethylene oligomerization in the presence of some catalytic systems based on zirconium compounds is due to their multisite character and a multiroute mechanism of the process. The feasibility of switching the base multiroute multisite multifunctional catalyst systems to monofunctional operation with a narrow molecular-mass distribution (MMD) of oligomerization products was shown using zirconyl carboxylate systems as an example. A comparative evaluation of the kinetic parameters of individual ethylene oligomerization steps and an analysis of the behavior of the MMD in the presence of three different catalyst systems were performed. A possible mechanism of regulation of the character and width of the MMD of the oligomerization products is discussed.