The linear viscoelastic behaviour of a series of mPE/LDPE blends was evaluated. Newtonian viscosity showed slight positive deviation from the double reptation model, which assumes miscibility or, at least, cooperative relaxation between the mixed species. This feature is typical of emulsion-like polymer blends and is attributable to additional relaxation processes that occur at low frequencies associated with deformability of the dispersed phase. Close agreement between data obtained by applying the Palierne model for emulsions of two viscoelastic liquids and experimental data was only shown for the blend of lowest LDPE content. Good predictions were derived for the higher LDPE contents, when partial miscibility of the components was assumed. In these cases, the viscoelastic response can be modelled through a hybrid model that takes into account the double reptation approach in the miscible phase models. Contrary to other heterogeneous blends, the blends examined here do not show an enhanced elastic character. This behaviour is probably due both to the extremely different relaxation times of the phases in the blends rich in mPE, and to the partial miscibility of the components in the blends of high LDPE content. (C) 2003 Kluwer Academic Publishers.