Let S-n(c) denote the n-dimensional Euclidean sphere of constant sectional curvature c and denote by CPn(c) the complex projective space of complex dimension n and of holomorphic sectional curvature c. In this paper, we obtain some characterizations of the manifolds S-2(c) x S-2(c'), S-4(c) x S-4(c'), CP2(c) x CP2(c') by their spectrum.