The modifications induced by an excimer laser irradiation at 193 nm or 248 nm on organic surfaces, below their ablation threshold, were investigated for different kinds of polymers such as: PEEK (Polyether Etherketone), PC (Polycarbonate), PET (Polyethylene terephtalate). Treatments were carried under argon or air at different laser fluences. Treated surfaces were characterized by XPS (X-rays Photoelectron Spectroscopy) and surface wettability measurements. For, all the studied polymers, the results shows that the surface modifications first depended on the laser wavelength. Surface oxidation occurred at 193 nm, leading to the formation of polar groups (carbonyls, carboxyls, hydroxyls) and inducing an increase of the surface energy. Treatments at 248 nm never induced any oxygen enrichment of the surface. This is due to the loss of oxygen by CO or CO2 desorption at this wavelength.