The fluid phase equilibria (liquid-liquid demixing behavior (LLE)) of mixtures of ionic liquids of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide family, [C(n)mim][NTf2], with 2-methylpropanol or n-octanol were investigated. Binary mixtures of [C(4)mim][NTf2] + alcohol and [C(6)mim][NTf2] + alcohol were compared to pseudobinary mixtures of (0.5[C(2)mim] + 0.5[C(6)mim])[NTf2] + alcohol and (0.5[C(2)mim] + 0.5[C(10)mim])[NTf2] + alcohol, respectively. Additionally, the presence of water in the studied alcohols or as a third component in the system was analyzed in order to check any possible deviation from the LLE observed for the anhydrous systems. Systems containing small fractions of ionic liquid show similar LLE between the corresponding binary and pseudobinary systems; however, large differences are observed in the presence of water when the IL mass fraction is increased.