This research aims at numerical study of fluid flow and heat transfer through microchannels having superhydrophobic surfaces consisting of aligned and staggered micropost patterns in the fully developed laminar flow regime. In this work, at the condition of constant surface heat flux, Poiseuille number, Nusselt number and also overall microchannel performance are examined at relative module width of Wm = 0.01, 0.1 and 1, cavity fraction range of Fc = 0.1 to 0.9 and Reynolds numbers of Re=10 and 100. In order to validate the current results, comparisons are made with theoretical and experimental approach and good agreements are observed. Numerical findings show that the staggered pattern is capable of producing higher frictional resistance and better thermal transport than the aligned structure. It is shown that an increase in the cavity fraction leads to a decrease in the Poiseuille and Nusselt numbers for the two micropost structures and this decrease becomes pronounced with increasing the relative module width. Results indicate that for the two micropost patterns, the role of increase in the relative module width is to decrease the Poiseuille and Nusselt numbers. It is found that the staggered arrangement could lead to higher overall performance than the corresponding aligned structure and enhancement in the performance becomes remarkable at high values of relative module width. Numerical findings indicate that for each micropost structure, an increase in the Reynolds number causes the microchannel overall performance to increase and the highest overall performance is attained at high relative module width and cavity fraction values.