Inonotus rickii (Pat.) Reid is a pathogenic wood-decaying fungus that causes severe decay in several ornamental urban trees in Europe. It has been known to occur on different hosts in Sicily (Italy) since 1985, and in Rome (Italy) since 2003. Some physical and mechanical wood features were studied according to the standards in order to propose an investigation methodology to set a deterioration ranking of urban trees. In this phase of the study, Celtis australis L., Acer negundo L., Acer campestre L., Robinia pseudoacacia L., Tilia × vulgaris Hayne, Ulmus minor Mill., Platanus × acerifolia (Aiton) Willd. and Quercus ilex L. were studied. The data were analyzed using ANOVA and M-ANOVA tests to check the differences among the specimens. A risk matrix was created in order to combine the features that showed statistical differences between the control specimens and the inoculated specimens, in order to establish, in vitro, a degradation ranking among the wood species. The wood species which showed no in vitro durability to I. rickii, were the same ones that displayed susceptibility in the living trees.