A method for simultaneously laser shock peening opposite laser shock peening surfaces on opposite sides of an article, such as a gas turbine engine airfoil, with varying thickness using oppositely aimed laser beams and varying surface fluence of the laser beams over the laser shock peening surfaces as a function of the thickness of the article beneath each one of a plurality of laser shock peened spots formed by the beams on the surfaces. The fluence may be equal to the thickness multiplied by a volumetric fluence factor, the volumetric fluence factor being held constant over the laser shock peening surface. The volumetric fluence factor may be in a range of about 1200 J/cm3 to 1800 J/cm3 and more particularly about 1500 J/cm3. Laser beam energy may be varied with a computer program controlling firing of the laser beam.