A maximal independent set is an independent set that is not a proper subset of any other independent set. A connected graph (respectively, graph) G with vertex set V(G) is called a quasi -tree graph (respectively, quasi-forest graph), if there exists a vertex x ∈V ( G) such that G - x is a tree (respectively, forest) . The purpose of this paper is to determine the largest number of maximal independent sets among all quasi- tree graphs and quasi -forest graphs containing no cycle of length three, respectively. Additionally, extremal graphs achieving these values are also given.