A new mathematical method has been proposed to evaluate the effect of inlet velocity on the performance parameters of cyclone using previous mathematical models. Collection efficiency, as a function of inlet velocity, is expressed with a new relation in terms of cyclone pressure drop. Effect of inlet velocity for different cyclone geometries and cyclone wall surface roughness is investigated. A trade off between higher collection efficiency and lower pressure drop is made. Increasing the inlet velocity more than a specific value does not necessarily lead to higher separation efficiency of finer particles, but also causes higher pressure drop in cyclones. Comparison of the calculated results with experimental findings confirmed the applicability of the model. (C) 2011 Elsevier B.V. All rights reserved.