The diffusivity of carbon dioxide and hydrogen sulfide was studied in five ionic liquids containing two different cations and four anions, namely, 1-ethyl-3-methylimidazolium (emim) based ionic liquids with bis-(trifluoromethyl)sulfonylimide (NTf2) anion and 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate, (eFPT) as well as 1-(2-hydroxyethyl)-3-methylimidazolium (hemim) based ionic liquids (ILs) with different anions, viz. hexafluorophosphate (PF6), trifluoromethanesulfonate (OTf) and bis(trifluoromethyl)sulfonylimide (NTf2). Experimental trials were carried out at temperatures of 303.15, 313.15 and 323.15 K and low initial pressures by means of semi-infinite volume method. The results show that the diffusion coefficients of CO2 and H2S in RTILs increase with increasing temperature, but with different orders, and the diffusivity of CO2 and H2S in (emim) based ILs is greater than that in (hemim) based ILs. In addition, the measured diffusion coefficients of CO2 and H2S have been fitted through Wilke-Chang empirical equation. (C) 2019 Elsevier Ltd.