Disclosed is a photoresist composition having a good sensitivity and residual layer characteristic and a method of forming a pattern using the same. The photoresist composition includes 5-30% by weight of a polymer resin, 2-10% by weight of a photosensitive compound, 0.1-10% by weight of a sensitivity enhancing agent, 0.1-10% by weight of a sensitivity restraining agent and 60-90% by weight of an organic solvent. A photoresist layer is formed by coating the photoresist composition on a substrate and then drying the coated photoresist composition. Then, thus obtained photoresist layer is exposed by using a mask having a predetermined pattern. Then, a photoresist pattern is formed by developing thus exposed photoresist layer. The photoresist pattern exhibits a uniform layer thickness and critical dimension.