The impact of eccentricity of the vortex finder with deviations in the range of 4-10% on the flow pattern and performance of gas cyclone was studied. The Eulerian-Lagrangian approach in conjunction with the Reynolds stress turbulence model (RSM) of the ANSYS-FLUENT 15 code was used in these simulations. It was found that with increasing deviation of vortex finder up to 10%, the tangential velocity was increased. The maximum tangential velocity obtained for the radial profiles was 1.8 times that of the inlet velocity and the lowest tangential velocity was 1.58 times that of the inlet velocity. The maximum periodic variation in axial and tangential velocities was in the free vortex (central portion of the cyclone). It was shown that increasing the eccentricity of the vortex finder led to an increase in the intensity of oscillation of the axial velocity. For 6% eccentricity, the axial velocity was reduced due to a decrease in the oscillation rate downstream of the cyclone, which is a major factor affecting the cyclone performance. The pressure drop was also increased with increasing eccentricity of the vortex finder. It was found that the gas cyclone with an eccentricity of 8% was more efficient for droplets larger than 1 gm. In this case, also the liquid film flow does not occur on the cyclone wall. (C) 2017 Elsevier B.V. All rights reserved.