Let T be a tree that is embedded in the plane and let Δ, ε ＞ 0 be real numbers. The aim is to preprocess T into a data structure, such that, for any query polygonal path Q, we can decide if T contains a path P whose Frechet distance δ_f{P, Q) to Q is less than Δ. We present an efficient data structure that solves an approximate version of this problem, for the case when T is c-packed and each of the edges of T and Q has length Ω(Δ) (not required if T is a path): If the data structure returns NO, then there is no such path P. If it returns YES, then 6f{P,Q) ≤ 2~(1/2)(1 + ε)Δ if Q is a line segment, and δ_{P, Q) ≤ 3(1 + ε)Δ otherwise.
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