A lot of research has been carried out to assess web-based courses. In many studies the concern has been the students' satisfaction and achievement in web-based courses and traditional face-to-face courses, and the comparison between the two. Other studies have focused on the development of web-based courses to meet the requirements of educational institutes. Studies about students' cognitive styles may be important for the designers of web-based courses because of the potential to enhance learning. However, the relationship between the students' cognitive styles and their satisfaction and achievement has not been researched fully and the implications are inconclusive. The aim of this study is to investigate the relationship between students' cognitive styles, their satisfaction, achievement, and their way of using a web-based course. Cognitive Styles Analysis (CSA) by Riding and Rayner [11] was selected as the instrument to determine whether students were field-dependent or field-independent. Students' attitudes toward using WebCT (Web Course Tools) were measured by a questionnaire specially designed for this intention. Students' activities on WebCT were observed through the tracking system which provided information about students' use of every tool and page on WebCT. The study does not provide data to support a relation between students' cognitive style and their use of online learning environments such as WebCT. However cognitive style seems to have an effect on student achievements.