For convex co-compact hyperbolic quotients X = Γ\H n+1 , we analyze the long-time asymptotic of the solution of the wave equation u(t) with smooth compactly supported initial data f = (f 0 , f 1 ). We show that, if the Hausdorff dimension δ of the limit set is less than n/2, then. We explain, in terms of conformal theory of the conformal infinity of X, the special cases δ ∈ n/2 − N where the leading asymptotic term vanishes. In a second part, we show for all ǫ > 0 the existence of an infinite number of resonances (and thus zeros of Selberg zeta function) in the strip {−nδ − ǫ < Re(λ) < δ}. As a byproduct we obtain a lower bound on the remainder R(t) for generic initial data f .