Solubilities of CO2 in eight hydroxyl ammonium ionic liquids 2-hydroxy ethylammonium formate (HEF), 2-hydroxy ethylammonium acetate (HEA). 2-hydroxy ethylammonium lactate (HEL), tri-(2-hydroxy ethyl)-ammonium acetate (THEAA), tri-(2-hydroxy ethyl)-ammonium lactate (THEAL), 2-(2-hydroxy ethoxy)-ammonium formate (HEAF), 2-(2-hydroxy ethoxy)-ammonium acetate (HEAA) and 2-(2-hydroxy ethoxy)ammonium lactate (HEAL) at the temperatures ranging from 303 to 323 K and the pressures ranging from 0 to I I MPa were determined. The solubility data were correlated using Krichevisky-Kasarnovsky equation, from which Henry's constants and the partial volumes of CO2 at different temperature were obtained. Results showed that Krichevsky-Kasarnovsky equation can correlate the solubilities of CO2 in these hydroxyl ammonium ionic liquids (ILs) well. Comparison showed that the solubility of CO, in these eight hydroxyl ammonium ionic liquids was in sequence: THEAL > HEAA > HEA > HEF > HEAL > THEAA approximate to HEL > HEAF (c) 2007 Elsevier B.V. All rights reserved.