Several refinements of norm and numerical radius inequalities of bounded linear operators on a complex Hilbert space are given. In particular, we show that if A is a bounded linear operator on a complex Hilbert space, then (equation presented) where k k, w.( ) and c( ) are the operator norm, the numerical radius and the Crawford number, respectively. Further, we prove that if A; D are bounded linear operators on a complex Hilbert space, then (equation presented) where jAj2 = A*A and jDj2 = D*D. This is a refinement of a well-known inequality obtained by Bhatia and Kittaneh.