One of the materials which has been used for rehabilitation and strengthening of structures in recent years is FRP composites (Fiber Reinforced Polymer). Their numerous advantages such as high tensile strength, ease of application and corrosion resistance have given rise to their application in strengthening a wide array of structures especially reinforced concrete members. Nevertheless, a major issue of concern in flexural strengthening of reinforced concrete beams with FRP laminates is their debonding off the concrete substrate, which leads to premature failure of the structural member thus strengthened. Surface preparation of concrete before attaching FRP sheets is considered as a suitable method to postpone debonding, but with limited effects. Grooving is an innovative technique to overcome debonding of FRP laminates from concrete surface, which has been recently used in Isfahan University of Technology (IUT), Iran. In this study, the effect of some factors influencing the grooving capability aiming at reducing the debonding potential of FRP sheets from the concrete surface is addressed. These factors include the width and the depth of the grooves. The experimental specimens used in this study included about 140 prism specimens of dimensions 100×100×500 mm subjected to 4-point flexural loading. Having been grooved on the surface, the specimens were reinforced with CFRP sheets and underwent the four-point flexural test so as to measure the ultimate loading capacity. The results indicate that debonding can be completely averted or at least to a large extent limited by considering specified width and depth for the grooves. Keywords: Debonding, Fiber Reinforced Polymer (FRP), Grooves, Surface preparation. .