This paper reports a numerical simulation on natural convection occurring in an irregular porous cavity. Three combinations of thermal boundary conditions are considered, involving conditions of adiabatic wall and/or isothermal heating. The horizontal upper wall is isothermally cooled and the other walls are considered as adiabatic. The steady-state regime is examined for several intensities of the buoyancy effects due to temperature variations. The effects of thermal boundary conditions on the flow pattern and temperature distributions are studied. Global and local Nusselt numbers are reported for the cooled and heated walls. Contour maps illustrate aspects of the fluid flow and temperature fields.