The first part of this paper deals with the concept of multi-word lexical units and the delimitation of their basic types in the Pralex lexical database, including the analysis of some terminological and conceptual issues. After a short preview of the approaches to the lexicographical treatment of multi-word lexical units in contemporary monolingual dictionaries, the second part of this paper deals with the database processing of multi-word lexical units, both with the general rules of their treatment in the Pralex lexical database and with the specific rules of treatment of one of two basic types of multi-word lexical units, i.e. multiple-word namings.