A counter-cone in cyclones is frequently used in a great number of practical applications. The primary function of a counter-cone is to counteract the extension of the end of the vortex downward to the bottom of the hopper and to prevent the re-entrainment of the previously separated solids. However, a counter-cone also affects the gas flow in a cyclone; hence its location should be taken into account in this respect. The presented paper shows that the appropriate location of a counter-cone in a cyclone can improve its efficiency. In an approximate way, the optimal position of a counter-cone can be calculated based on the commonly known Barth model. The optimal position is the function of several variables including the coefficient of friction. The friction coefficient depends on the surface roughness and flow conditions including loading of solids which can vary during the operation of the device. The obtained calculations were verified with laboratory experiments in which a counter-cone was placed over the outlet of the solids. This study shows that the appropriate position of a counter-cone facilitates the efficiency of the cyclone. In the investigated cyclone, the improvement of efficiency was achieved by moving the counter-cone upwards.