The library catalog is considered an important tool to provide library users with conveniences making a search for necessary information. Accordingly, the purpose of this study is to investigate "behaviors and attitudes" of library users in a university library using online and card catalogs together, to compare their distinctions between online and card catalogs and then to bring about reforms for the development of future cataloging, thereby improving the utilization of online catalog and its service expansion. For this, this paper carried out a survey research which was randomly questionaired 280 library users of four universities in Seoul from March 28th to April 16th 1996. Major findings are as follow : 1. Library users tended to use more online catalog(50.0%) than card catalog (21.9%). 2. The main reasons the library users us online catalog were time saving(24.0%), convenience of use(21.3%), multiple searching possibility (16.2%), and the preferences of card catalog were location of library materials(34.6%), time saving(17.5%), Bibliographic information(14.9%). 3. The major access points which library users utilized mostly in their online catalog are title(30.3%), author(29.2%) and subject heading (17.6%), and for card catalog, title(40.5%), author(34.6%) and call no.(11.1%). 4. The methods library users learned to use online catalog are terminal screen(44.7%), online manual(26.1%), and for card catalog, library orientation(42.6%), librarian's help(18.5%). 5. It was shown that library users were not mostly satisfied about their searching results: the users satisfied with online catalog in the order of partly(46.2%), as expected(42.3%), more than expected(10.4%), and with the card catalog in the order of partly(54.6%), as expected(27.3%), more than expected(10.4%). It was found that although library users preferred online catalog more than card catalog, 54.8% of the total catalog users were not satisfied about the search results they have had. 6. The items which library users want to add to online catalog are catalogs of materials other libraries have(41.6%), catalogs of the materials the library has(29.3%), titles of serial articles(17.7%). And the additional services library users want are checking function of loan materials and reservation of materials(15.5%), subject headings(14.5%), more terminals(13.4%), catalog use explanations(12.9%), multiple access points(11.0%), searching function of contents, abstracts, and indexes(9.6%). Considering the fact that library users tend to use more favorably online catalog than card catalog and the trend that library change from card catalog to online catalog, it is strongly recommended to su n.0, pply students with formal and informal training programs for online catalog use.talog use.