PURPOSE: The Korean Society of Coloproctology holds its annual colorectal awareness month every September. This study analyzed the users and the contents of Korean tweets regarding colorectal cancer and estimated the transmissibility of the awareness campaign among Twitter users. METHODS: Prospective data collection was employed to accumulate Korean tweets containing the keywords "colorectal cancer," "colorectal cancer awareness campaign," "gold ribbon," and/or "love handle," from August 1 to September 30, 2014. Twitter users and contents were analyzed, and the credibility of information-sharing tweets throughout the study period was evaluated. RESULTS: In total, 10,387 tweets shared by 1,452 unique users were analyzed. As for users, 57.8% were individuals whereas 5.8% were organizations/communities; spambots accounted for a considerable percentage (36.4%). As for content, most tweets were spam (n = 8,736, 84.1%), repetitively advertising unverified commercial folk remedies, followed by tweets that shared information (n = 1,304, 12.6%) and non-information (n = 347, 3.3%). In the credibility assessment, only 80.6% of the information-sharing tweets were medically correct. After spam tweets had been excluded, a significant increase was seen in the percentage of information-sharing tweets (77.1% to 81.1%, P = 0.045) during the awareness campaign month. CONCLUSION: Most Korean tweets regarding colorectal cancer during the study months were commercial spam tweets; informative public tweets accounted for an extremely small percentage. The transmissibility of the awareness campaign among Twitter users was questionable at best. To expand the reach of credible medical information on colorectal cancer, public health institutions and organizations must pay greater attention to social media.