Viscosity is an important physical property of ionic liquids (ILs). The viscosities of ILs are relatively high, when compared to those of common organic solvents. It is known that the viscosities of ILs vary widely depending on the type of cation and anion present. A high correlate and simplified quantitative structure-property relationships (QSPR) would offer a prediction possibility of viscosity for the design of new ILs. This study aimed to develop a simplified prediction model for viscosity of imidazolium-based ILs using QSPR coupled with the descriptors of group contribution. Considering temperature, molecular weight, and the number of the branched-chain carbon atoms in the imidazole ring, we formulated a mathematical relationship between the viscosity of imidazolium-based ILs and the descriptive parameters of anions and cations. The importance of molecular weight on the viscosity of imidazolium-based ILs was reflected in our group contribution method QSPR as a novel parameter. The correlation coefficient between the reported literature values and the predicted values of viscosity was R-2 = 0.9888. By performing QSPR, we hope to accelerate the development process of new imidazolium-based ILs with desired viscosity. (C) 2013 Elsevier B.V. All rights reserved.