Аннотация:We obtain a criterion given in terms of the Fourier-Haar co-efficients for the function f(x1, x2) to belong to the net space Np̄, q̄(M) and to the Lebesgue space Lp̄[0, 1]2 with mixed metric, where 1 < p̄ < ∞,0 < q̄ ≤ ∞, p̄ =(p1, p2), q̄=(q1, q2) and M is the set of all rectangles in ℝ2. We prove the Hardy-Littlewood theorem for multiple Fourier-Haar series.