For the design and development of new processes of gas sweetening using ionic liquids (ILs), as promising candidates for amine solutions, an amazing model to predict the solubility of acid gases is of great importance. In this direction, in the current study, the capability of artificial neural networks (ANNs) trained with back propagation (BP) and particle swarm optimization (PSO), to correlate the solubility of H2S in 11different ILs have been investigated. Different structures of three-layer feed forward neural network using acentric factor (omega), critical temperature (T-c), critical pressure (P-c) of ILs accompanied by pressure (P) and temperature (T), as input parameters, were examined and an optimized architecture has been proposed as 5-9-1.Implementation of these models for 465 experimental data points collected from the literature shows coefficient of determination (R-2) of 0.99218 and mean squared error (MSE) of 0.00025 from experimental values for PSO-ANN predicted solubilities while the values of R-2=0.95151 and MSE=0.00335 were obtained for BP-ANN model. Therefore, through PSO training algorithm we are able to attain significantly better results than with BP training procedure based on the statistical criteria. (C) 2014 Elsevier B.V. All rights reserved.