The appearance of skin after surgery plays an important role in patient's self confidence and life style. In fact, Keloids and hypertrophic scars are abnormal wound responses appearing in predisposed individuals after surgery. Among different kind of lasers, used to improve the appearance of hypertrophic scars and keloids, pulsed dye laser is now being used successfully in treatment of scars. Pulsed dye laser is effective in improving the color, height, texture, and elasticity of scars. Also, treatment with this technique is noninvasive, minimally uncomfortable, and requires no anesthesia. This study will assess the efficacy and safety of different onset times of treatment with pulsed dye laser on improvement of surgical scars.