The solute diffusion in boundary layer flow of an incompressible fluid through a porous medium over a porous flat plate with first-order chemical reaction and with variable surface concentration is studied. The reaction rate of the solute is also takenasvariable. The self-similar ordinary differential equations are obtained from the governing partial differential equations using similarity transformations, and then those self-similar equations are solved by shooting technique using forth-order Runge-Kutta method. The analysis shows that the velocity increases with the increase of permeability of the porous medium, whereas the concentration decreases. The thicknesses of momentum and solute boundary layers reduce for suction, and the effect of blowing is opposite. For the inverse variation of wall concentration along the surface, mass absorption at the surface is found in all cases, and in direct variation mass transfer is found. For increase of both the Schmidt number and the reaction rate parameter, the concentration as well as the solute boundary layer thickness decreases.