Methanolic solutions of poly(methacrylic acid) adjusted to various degrees of neutralization with lithium methoxide were investigated by photon correlation spectroscopy. The results obtained are compared with the dynamic behaviour of aqueous solutions. The influence of the solvent dielectric permittivity ε on the polyelectrolyte dynamics is discussed ( ε = 31.4 and 78.5 for methanol and water, respectively). While two diffusive modes corresponding to the dynamics of individual chains and of multi-chain domains can be observed in aqueous solutions, no domains are present in methanolic solutions. The only observable mode (Nernst-Hartley coupled diffusion of polyions and counterions) depends anomalously on the degree of neutralization, indicating the existence of ‘excess counterion counterion condensation’. Both phenomena cannot be explained by the classical polyelectrolyte theory, which takes into account only the change of the dielectric permittivity. The role of counterions in these effects is stressed. They influence the solvent quality and cause a chain collapse reflected in excess counterion condensation. The absence of domains in methanol is ascribed to the relatively low osmotic activity of counterions.