In this paper our focus is to study necessary optimality conditions for nonsmooth vector optimization problems in Banach spaces. Since in most infinite dimensional spaces the natural ordering cone has an empty interior it becomes quiet difficult to study vector optimization problems. This is due to the fact that we do not have powerful scalarization techniques in such a situation. In this paper we show how we can overcome such difficulties by using the notion of dilating cones. © 2008 Yokohama Publishers.