Dissolution rate of polymer has known as one of the most profound factors to determine profiles of DUV resists. A novel copolymer, poly[4-hydroxystyrene-co-4-(3-cyano-1,5-di-tert-butyl carbonyl pentyl styrene)] (PHSCBPS), was prepared and blended with poly(4-hydroxystyrene-co-4-(1-ethylethoxystyrene)) (EEPHS) to study the effect of dissolution rate on the KrF resist profile. The dissolution rates of the blends in aqueous alkaline solution were measured by dissolution rate monitor (DRM). Molecular weight and polydispersity were measured by GPC. Without altering other components of the resist, the profile was clearly affected by the dissolution rates of the polymer blends. In this paper we will describe resist profile change according to dissolution rate, molecular weight and polydispersity of polymer blend. For given blends, the best and optimum resist profile was found in the range of 200~300 Angstroms/min dissolution rate, 12,000 of molecular weight and 1.2~1.3 of polydispersity. In case of PAG, profile of KrF resist is also influenced by counter ion of PAG. Based on the results, high performance KrF resist composition was found by incorporating appropriate photo acid generator (PAG) and other additives. Optimized resist produced rectangular profile without losing process margin and resolution.