Mixed convection flows in a lid-driven square cavity filled with porous medium are studied numerically using penalty finite element analysis for uniformly heated bottom wall, linearly heated side walls or cooled right wall. The top wall is well insulated and set with uniform velocity. The relevant parameters in the present study are Darcy number (Da = 10- 5 s(-) 10- 3), Grashof number (Gr = 103 s(-) 105), Prandtl number (Pr = 0.015-10) and Reynolds number (Re = 1-102). The isotherms are generally symmetric at smaller Pr irrespective of Da and Re at Gr = 105 for linearly heated side walls. The isotherms are also almost symmetric at small Re with higher Gr(Gr = 105) and Da(Da = 10- 3) and natural convection is found to be dominant whereas the isotherms are compressed near the left and bottom walls at higher Re for linearly heated side walls. Compression of isotherms and dominance of forced convection is also observed at Re = 102 for linearly heated left wall and cooled right wall. The local Nusselt number of the bottom wall (Nub) for low Da is almost constant whereas Nub for higher Da and Pr shows non-monotonic variation at Re = 10 and an overall decreasing trend is observed at Re = 102 for linearly heated side walls. The local Nusselt numbers of left and right walls (Nul and Nur) increase for Da = 10-3 and Pr = 0.7 whereas oscillatory trend is observed at Re = 10-102 and Pr = 10. For linearly heated left wall and cooled right wall, Nub increases from the left edge towards the right edge of the bottom wall for both cases Re = 10 and 102 irrespective to Pr and Da. It is also observed that Nur for higher Pr and Da is found to increase monotonically at both Re = 10 and 102 and Nul show non-monotonic trend for higher Pr and Da at Re = 10 whereas for Re = 102, Nul increases monotonically. Average Nusselt numbers fenced(over(Nub, -), over(Nul, -), over(Nur, -)) are found almost invariant with Gr for low Pr with all Da for linearly heated side walls or cooled right wall. On the other hand, over(Nub, -) is found to vary exponentially at higher Pr and Da and oscillations inover(Nul, -) and over(Nur, -) are observed for Re = 10 whereas increasing trend is observed for over(Nul, -) and over(Nur, -) for Re = 102 for both linearly heated side walls or cooled right wall. © 2010 Elsevier Ltd. All rights reserved.