The primary purpose of this study was to examine the effectiveness of three types of instructional media to deliver online lectures for motivation and content-related comprehension in the online course of Health Counseling Psychology. This study examined whether one instructional media (e.g., video-based instruction) was better than another (e.g., audio-based instruction or text-based instruction) in motivation and content-related comprehension. The total of 237 online students majoring in the field of counseling and psychology at the Seoul Cyber University in Korea participated in this study in fall 2011. The participants were randomly assigned to one of three treatment groups (e.g., video-based instruction, audio-based instruction, and text-based instruction without using streaming media). Finally, the total of 172 students completed the two-week online lectures for three treatment groups and took two posttests on comprehension and motivation. This study used an experimental design with quantitative data. A between-groups experimental design with the short form of IMMS and comprehension test was employed. For the first and second research questions, a one-way ANOVA was conducted to determine if there were significant different means in student motivation and comprehension across three different types of instructional media. According to the findings of this study for students' motivation, instructional video as a means of streaming media was a more effective instructional medium than text to enhance students' motivation in an online course. In addition, streaming media (e.g., video clips and audio files) were efficient instructional technology tools to motivate online students positively in diverse online settings. The streaming media (e.g., video and audio) in diverse instructional designs can be used as a means of instructional delivery tools to help online students to be successfully motivated in online learning. According to the results in students' comprehension, three different types of instructional media had no different effect on students' comprehension in online learning. In the three different types of instructional design with streaming media or web-based text only, using instructional technology tools did not affect the student comprehension as a means to increase student understanding cognitively in an online educational setting. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]