Let µ be a positive Borel measure on the interval [0, 1). The Hankel matrix H µ = (µ n,k ) n,k≥0 with entries µ n,k = µ n+k , where µ n = [0,1) t n dµ(t), induces formally the operator(1−tz) 2 dµ(t) for all in Hardy spaces H p (0 < p < ∞), and among them we describe those for which DH µ is a bounded(resp.,compact) operator from H p (0 < p < ∞) into H q (q > p and q ≥ 1). We also study the analogous problem in Hardy spaces H p (1 ≤ p ≤ 2).