Experimental densities of two ionic liquids (ILs), 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C(4)C(1)Pyrr][NTf2]) and 1-(2-methoxyethyl)-1-methyl-pyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([C(1)OC(2)C(1)Pyrr][(C2F5)(3)PF3]), were measured over a broad temperature and pressure range, i.e. from (278.15 to 398.15) K and up to 120 MPa, respectively. The isobaric thermal expansion coefficient of the two ILs was determined from these measurements finding a non-monotonous behaviour over the entire pressure range. The density values obtained were used to analyse the prediction ability of the methods proposed by Gardas and Coutinho and by Jacquemin et al. Furthermore, the influence of the cation and anion structure on the densities and the isothermal compressibilities was analyzed, also considering literature values. (C) 2012 Elsevier Ltd. All rights reserved.