abstract: We study a prescribed Q-curvature problem in the Euclidean space R4, assuming to have power-type and sign-changing Q-curvature. Geometrically, finding a solution to this problem, corresponds to find a metric conformal to the Euclidean one on R4, which has the assigned prescribed Q-curvature. First, under suitable assumptions, we prove existence of non-normal solutions to our problem, extending in this way some previous results. Then, we prove a classification result, which allows us to characterize solutions in terms of the behavior at infinity of the scalar curvature of the associated conformal metric. We also present the corresponding problem on the plane.