In this thesis the structure of polyelectrolyte (PE) solutions in ionic liquids (ILs) and mutual influence of bothcomponentsthe local structure of the latter in the presence of PEs are studied. X-ray and neutron scatteringtechniques have been mainly used for the present investigation. In a first part, the ability of considered ILs toform clusters at nanoscale is demonstrated. In a second part, the influence of the nature of counterions andthe solvent on the polystyrene sulfonate (PSS) behavior in solution is tackled. PSS average conformation anddispersion state in aqueous and organic media are then explored in a third part. A similar investigation, carriedout on the specific case of PSS in IL media, is described in a fourth part. Finally, other polymers, both chargedand neutral, in IL solutions are considered in a fifth and last part.