A laboratory study has been undertaken to elucidate the influence of structural parameters of polymer/electrolyte systems commonly used for the formulation of water-based drilling fluids on their performances as filtrate reducers or cuttings dispersion inhibitors. The dependence of properties of bentonite/polymer/electrolyte systems on polymer molecular characteristics has been studied. The results indicate that polymer dimensions which depend on both salinity and polymer molecular weight have a major influence on the efficiency in inhibiting cuttings dispersion. Filtration properties of the investigated model fluids have been found to be strongly dependent on polymer/bentonite interactions: an increase in molecular weight of polymeric additives can induce clay particle flocculation resulting in poor filtration control whereas an increase in polymer negative charges improves bentonite dispersion and thus filtration properties.