Modern composite materials, made on the basis of non-metallic continuous fibers are increasingly used in civil engineering, in particular to strengthen building structures. In strengthening of RC structures the utilization of externally bonded FRP composites is only up to 35% because of the pilling-off failure mechanism. This problem can be solved by the use of pre-tensioned composite laminates. Due to more complex behavior, the strengthening of structures using prestressing technology needs a careful design approach and a full understanding of the behavior of both the materials and elements. The advantages and risks of the presented technology, which may determinate the success of the entire project, are highlighted in the article.