In this paper, we first show that the power domination number of a connected 4-regular claw-free graph on n vertices is at most n+1 5 , and the bound is sharp. The statement partly disprove the conjecture presented by Dorbec et al. in SIAM J. Discrete Math., 27:1559-1574, 2013. Then we present a dynamic programming style linear-time algorithm for weighted power domination problem in trees.Let G = (V, E) be a connected, simple graph with vertex set V = V (G) and edgeWe denote K i,j the complete bipartite graph with two partite sets of cardinality i and j, respectively. A claw-free graph is a graph that does not contain a claw, i.e., K 1,3 , as an induced subgraph. We say a subset of V (G) an independent set if no two vertices of the set are adjacent in G. Let x and y are two vertices of G. Denote by d(x, y) the distance of x and y in G. We say a subset of V (G) a packing if no two vertices in the set of distance less than three in G. For two graphs G = (V, E) andthen G and G ′ are disjoint. For any vertex subset X of G, let G − X = G[V \ X] and for X = {x} let G − x = G − {x} for short. For notation and graph theory terminology not defined herein, we in general follow [7]. The original definition of power domination was simplified to the following definition independently in [9, 10, 12, 17] and elsewhere. Definition 1.1 Let G be a graph. A set S ⊆ V (G) is a power dominating set (abbreviated as PDS) of G if and only if all vertices of V (G) have messages either by Observation Rule 1 (abbreviated as OR 1) initially or by Observation Rule 2 (abbreviated as OR 2) recursively.OR 1. A vertex v ∈ S sends a message to itself and all its neighbors. We say that v observes itself and all its neighbors. OR 2. If an observed vertex v has only one unobserved neighbor u, then v will send a message to u. We say that v observes u.Let G = (V, E) be a graph and S be a subset of V . For i ≥ 0, we define the set P i G (S) of vertices observed by S at step i by the following rules: