We consider the problem of finding positive solutions of the problem Δu − λu + u 5 = 0 in a bounded, smooth domain Ω in ℝ 3 , under zero Neumann boundary conditions. Here λ is a positive number. We analyze the role of Green’s function of −Δ + λ in the presence of solutions exhibiting single bubbling behavior at one point of the domain when λ is regarded as a parameter. As a special case of our results, we find and characterize a positive value λ * such that if λ − λ * > 0 is sufficiently small, then this problem is solvable by a solution u λ which blows-up by bubbling at a certain interior point of Ω as λ ↓ λ * .