Abstract: Photoresist compositions improving the quality of a photoresist pattern, methods for forming a pattern using the same, and methods for fabricating a semiconductor device using the same are provided. The photoresist composition includes a photosensitive resin, a photoacid generator, a photoacid-labile additive comprising a structure of Formula 1-1, and optionally a solvent: Ar2—Y-PG2??[Formula 1-1] wherein Ar1 is a substituted or unsubstituted aromatic ring, Y is an ester group, an oxycarbonyl group, an acetal group, an amide group, or a thioester group, and PG2 is a substituted or unsubstituted secondary alkyl group, a substituted or unsubstituted tertiary alkyl group, a substituted or unsubstituted alkoxyalkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted alkyloxycarbonyl group.