In this paper, by using the fixed point index method, we establish the existence of at least one or at least two positive solutions to the three-point boundary value problem for a second order differential equation with an advanced argument u" (t) + a (t) f (u (h (t))) = 0, t epsilon (0, 1), u(0) = 0, alpha u(q) = u(1), where eta epsilon (0, 1), alpha > 0, and 1 - alpha eta > 0. As an application, we also give an example to demonstrate our result. (c) 2005 Elsevier Ltd. All rights reserved.