The primary purpose of this study is to verify the difference of behavioural characteristics between the subject specialists and professional searchers in searching full-text databases. The major findings and conclusions from this study are summarized as follows. Analyses of Search questions(the degree of understanding with search questions, the degree of difficulty in selecting terms, and the degree of expectation of search results), search processes(the number of search terms used, the number of Boolean operators and qualifiers used, the number of documents browsed and the search time(the connecting time, time to spend per one output document, time to spend per one relevant output document) and search results(the searching efficiency(the number of relevant documents, the ,recall ratio and the precision ratio), the search cost(the total search cost. the search cost per one output document and the search cost per one relevant output document) and the degree of satisfaction with search results) are significantly different between the subject specialists and professional searchers in searching full-text databases