Photoresist polymers, and photoresist compositions using the polymer are disclosed. More specifically, photoresist polymers containing maleimide represented by Formula 1. Photoresist compositions including the photoresist polymers have excellent etching resistance, heat resistance and adhesiveness, and development ability in aqueous tetramethylammonium hydroxide (TMAH) solution. As the compositions have low light absorbance at 193 nm and 157 nm wavelength, they are suitable for a process using ultraviolet light source such as VUV (157 nm). wherein, 1, R1, R2, R3, R, R′, R″, R″′, X, a and b are defined in the specification.