The cyclones are one of the most known apparatus destined to the solid-gas separation. These equipments are used in the chemistry industry; its popularity is due mainly to the simplicity, low energy requirements and ability to operate at high temperatures and pressures. One of the aims of this work was to evaluate the influence of some geometrics variables in the performance of conventional cyclones and filtering cyclones. The chosen variables were: conic part length (Zc), the underflow diameter (Du), the overflow diameter (Do) and the finder length (Sc). The cyclones conventional and with filter were compared and it was observed that the introduction of a filter main in substitution to the metallic conic part of cyclones allows a appreciable reduction in the pressure drop and consequently a smaller consumption of energy. The efficiency in the new cyclone was a little smaller than the conventional equipment.