If µ is a positive Borel measure on the interval [0, 1) we let H µ be the Hankel matrix H µ = (µ n,k ) n,k≥0 with entries µ n,k = µ n+k , where, for n = 0, 1, 2, . . . , µ n denotes the moment of order n of µ. This matrix induces formally the operatorµ n,k a k z n on the space of all analytic functions f (z) = ∞ k=0 a k z k , in the unit disc D. This is a natural generalization of the classical Hilbert operator. In this paper we improve the results obtained in some recent papers concerning the action of the operators H µ on Hardy spaces and on Möbius invariant spaces.