Conceptual models are directly related to knowledge representation and should be capable of representing a context. These models should highlight the relevant objects in the domain, as well as their relationships and attributes, removing of the representation the objects that are not important for its consistency in relation to reality. Library and Information Science has been working on theoretical and methodological bases capable of providing for the construction of conceptual models, and therefore knowledge organization systems such as conceptual thesaurus. In Computer Science, whose focus is the representational possibility of communication between systems, seems to have been in recent years, perceptions that allow the modeling part of a domain with independent theories of a domain, like foundational ontologies, applying philosophical and cognitives theories to this process, providing ontological principles for classification of concepts. The aim of this study is, through comparative analysis, to verify if the theoretical and methodological bases used in the construction of conceptual thesauri can contribute to the conceptual development of foundational ontologies, pointing out the existing conceptual thesauri elements that must be observed in the construction of a foundational ontology. The study is based on the analysis of theoretical and methodological bases used in the construction of conceptual models of conceptual thesaurus, the Concept Theory of Ingetraut Dahlberg, Faceted Classification Theory of Shiyali Ramamrita Ranganathan, in Library and Information Science, and foundational ontologies, from the Unified Foundational Ontology (UFO-A), developed by Giancarlo Guizzardi, which is based on principles of Philosophy and Cognitive Sciences to build its conceptual model based on objects (endurants). It is concluded that Library and Information Science has theoretical and methodological bases (Concept Theory and Faceted Classification Theory) to build terminological instruments, like conceptual thesaurus, which constitutes a solid knowledge framework that can be created to allow an independent theory about a domain. The foundational ontologies have strong subsidies from Philosophy and Cognitive Sciences, allowing the real structure of a domain is represented in a consistent manner, being the holder of a semantic representation based on the real world, restricting their interpretations of concepts. The foundational ontologies allow the construction of a theory about the field, allowing to test and validate a conceptual model. It is understood that this study helps to make explicit the largest number of differences than similarities between these models and, consequently, between the instruments themselves.