This paper analyzes the possibility of optimizing the structure of cyclone separators through the application of an additional compartment in the form of a counter-cone. Analysis of studies published so far indicates that few of them concern such improvements for cyclone separators, and those that do focus solely on determining the effect of a counter-cone on the efficiency of solid particle separation. This paper also assesses the effect of a counter-cone on pressure drop. Furthermore, the risk of excessive agglomeration of particles in the lower area of the conical part of the cyclone due to the proposed structural modifications was assessed. Based on the obtained study results, was proposed a method for the determination of the optimum counter-cone location. Fifteen variants of geometric configurations of the counter-cone were tested using two study methods Computational Fluid Dynamics (CFD) and experimental research. The Reynolds-averaged Navier-Stokes equations with the Reynolds stress turbulence model (RSM) were used in the analysis. Cyclone separators from a real industrial installation, i.e. a kiln gas bypass system for cement clinker burning, were used for the research. This allowed for additional validation of the numerical models used and parametrization of calculation and boundary conditions. The application of a counter-cone was found to benefit the basic parameter characterizing cyclone separators, i.e. separation efficiency. (C) 2017 Elsevier B.V. All rights reserved.