Polymer surface modification using plasmas and excimer lasers was introduced, and the essential chemical reactions occurring in the surface modification process were described. The main chemical reactions in surface modification by plasma irradiation are hydrogen abstraction from polymer chains to form carbon radicals at the polymer chain and recombination between the carbon radicals and other radicals in the plasma to form functional groups. Therefore, the easier the hydrogen abstraction from polymers is, the more effective the surface modification. Surface modification by excimer lasers also proceeds with similar chemical reactions, hydrogen abstraction and recombination of carbon radicals with other radicals in the plasma. A new surface modification technique, remote plasma treatment, was proposed and applied for hydrophilic surface modification of poly (tetrafluoroethylene).