Maghemite (γ-Fe 2 O 3) nanoparticles (NPs) can be successfully dispersed in a protic ionic liquid, ethylammonium nitrate (EAN) by transfer from aqueous dispersions into EAN. As the aqueous systems are well controlled, several parameters can be tuned. Their crucial role on the interparticle potential and on the structure of the dispersions is evidenced : (i) The size of the NPs tunes the interparticle attraction monitoring dispersions to be either monophasic or gas-liquid like phase separated; (ii) The nature of the initial counterion in water (here sodium, lithium or ethyl ammonium) and the amount of added water (< 20% vol) modulate the interparticle repulsion. Very concentrated dispersions with a volume fraction around 25% are obtained thanks to the gas-liquid like phase separations. Such conclusions are derived from a fine structural and dynamical study of the dispersions on a large range of spatial scales by coupling several techniques: chemical analyses, optical microscopy, dynamic light scattering, magneto-optic birefringence and Small Angle Scattering.