Let α i ∈[0, ∞), ξ i ∈ (0,1) and ∑∞i=1α i ξ i <1. We study the existence of positive solutions to the boundary value problem
u''+a(t) f(u)=0, t ∈(0, 1),
u(0)=0, u(1)= ∑∞i =1 α i u ( ξ i ) ,
where α ∈ C([0, 1], [0, ∞)), and f:[0, ∞) → [0, ∞) is continuous. We show the existence of at least one positive solution if f is either superlinear or sublinear by applying a fixed-point theorem in cones.