Abstract. In this paper we consider existence, asymptotic behavior near the boundary and uniqueness of positive solutions to the problem divx(|∇xu| p−2 ∇xu)(x, y) + divy(|∇yu| q−2 ∇yu)(x, y) = u r (x, y) in a bounded domain Ω ⊂ R N × R M , together with the boundary condition u(x, y) = ∞ on ∂Ω. We prove that the necessary and sufficient condition for the existence of a solution u ∈ W 1,p,q loc (Ω) to this problem is r > max{p − 1, q − 1}. Assuming that r > q − 1 ≥ p − 1 > 0 we will show that the exponent q controls the blow-up rates near the boundary in the sense that all points of ∂Ω share the same profile, that depends on q and r but not on p, with the sole exception of the vertical points (where the exponent p plays a role).