Attitude has been understudied in the information systems (IS) field. Research interest in attitude has gone through ups and downs due to the lack of predictability of attitude for behavioral intention on using ICT. In this paper, we first clarify both conceptual and operational confusions on attitudes that may have caused the inconsistent and inconclusive results. Two different types of attitudes, attitude toward object and attitude toward behavior, are defined and their structures are discussed. Then we propose a theoretical model that details the relationships among attitude toward object, attitude toward behavior, and behavioral intention both for initial ICT use stage and for continued ICT use stage. A longitudinal study with mandatory use of a course management system is conducted. Results show that attitude toward behavior is a strong predictor of intention; attitude toward object (ICT) influences intention indirectly through attitude toward behavior; and intention during initial use has a strong positive effect on intention during continued use. In addition, the roles of previous attitudes on current attitudes are dependent on whether the current attitudes are about initial use or continued use.