Natural convection in a 2-D vertical cylinder containing an isotropic porous media with internal heat generation was studied numerically for assessing the effect of Darcy＇s law with and without the Brinkman extension on the streamlines, isotherms and Nusselt numbers. Two cases were analyzed: (1) insulated walls at the top and bottom of the cylinder and cooled external walls; (2) isothermally cooled walls at all external surfaces. The effect of the Brinkman extension was significant for high values of Da (10(-4)-10(-1)). In addition, the Nusselt number increases asymptotically as Da decreases. Also, four correlations for the average Nusselt number were derived.