In this paper we present own design of an indexing structure for general graph structured data called ?-index that allows an effective processing of special path queries. These special queries represent for example a search for all paths lying between two arbitrary vertices limited to a certain path length. The ?-index is a multilevel balanced tree structure where each node is created with a certain graph transformation and described by modified adjacency matrix. Hence, ?-index indexes all the paths to a predefined length l inclusive. The search algorithm is then able to find all the paths shorter than or having the length l and some of the paths longer then the predefined l lying between any two vertices in the indexed graph. We also present an experimental evaluation of the process of creating the p-index on graphs with different sizes and also a complexity evaluation of the search algorithm that uses the p-index.