Many bridges all around the world experience very hard environmental conditions, and due to the irregular maintenance effort, show different problems of cracking, concrete cover detachment and steel reinforcement wear and corrosion. In general, as a consequence of the polluted rain wetting, the problem is more evident in vertical structures than in the horizontal ones, and serious problems can arise when the piers and columns are very tall. In recent times, the solutions offered by composite materials have shown their effectiveness in the field of bridge maintenance. As a consequence of lightness and ease of installation they are particularly intended to the rehabilitation of tall slender structures. Furthermore, the externally bonded reinforcement offers a valid protection to chloride diffusion and rusting of steel rebar. In the paper some interesting cases in Italy and Bulgaria are briefly discussed in order to point out the key factors that promote the deterioration of concrete bridge structures. Afterwards, two very interesting strengthening works completed recently by using only externally bonded C-FRP reinforcement are presented and discussed. Finally, the main findings of an ongoing research on bridge slab strengthening are presented. The obtained results are based on an extensive experimental investigation carried out on slab specimens obtained by cutting an existing bridge 30 years old laying in the E45 Italian highway.