The purpose of this study is to investigate flexural behavior of one way RC slab with opening and applying strengthening to them by using CFRP strips. Size and location of opening on the slab are the main parameters that are investigated in this experimental research. Three different square opening with 300 mm, 400 mm and 500 mm side are tested. These openings are situated in two different places, bending and shear zone. Two series of test are done during experimental program. First set of experiments are done without strengthening and second set of test are done after strengthening with CFRP strips. Totally, thirteen test specimens are tested, including one reference specimen, six specimens without strengthening and six specimens with strengthening. CFRP strips are located around the openings along the specimen. Finally some evaluations of test results are done for determining the performance of strengthening techniques. Strength, stiffness, ductility and energy dissipation capacities of specimens are calculated and compared. In addition strain measurements are taken from CFRP strips and failure modes of specimen are investigated. By all these evaluations, the strengthening technique that can be applied easily, faster and required less workmanship is developed. Capacity values of the specimens are calculated according to ACI 440 Committee report and the results are compared with experimental results. (C) 2013 Elsevier Ltd. All rights reserved.