The permeability of wick microstructures plays crucial roles in the performance of heat pipes and vapor chamber since it affects the flow rate of the working fluid. In the present study the permeability of sintered particle wicks and microporous wicks with geometric inverse to sintered particles is investigated by numerical approach. Based on the numerical results, closed-form correlations are proposed for predicting the permeability of both sintered particle wicks and inverse wicks. The correlations are developed from the modified Kozeny-Carman's equation in which the Kozeny-Carman coefficient is given as an exponential function of porosity. The proposed correlations are shown to predict the previous experimental results well for an extensive parametric range. It is evident that the permeability of inverse wicks is significantly higher than that of conventional wicks due to the high porosity. (C) 2015 Elsevier Ltd. All rights reserved.