i* is a well known goal modeling framework, developed by a large and geographically dispersed research community. Currently, i* users tend to ascribe different and conflicting meanings to its constructs, leading to a non­ uniform use of the language, and consequently undermining its adoption. In previous works, we proposed ontological guidelines to support the creation of i* models, in an attempt to provide a solution to this problem. In this paper, we present an empirical study, to evaluate these ontological guidelines. Results show that for more experienced conceptual modelers, the ontological guidelines indeed support i* modeling. However, results are not as positive for non­experienced conceptual modelers.