496 Background: Patient-reported outcomes are typically collected through structured questionnaires. Patient web forums provide a unique opportunity for patients to spontaneously post their experiences and thoughts about diseases and treatments. This study explored the impact of colorectal cancer (CRC) treatments in these forums. Methods: This was a cross-sectional qualitative analysis of web data. Two of the most active CRC web forums were identified using 4 criteria: site active for > 5 years, > 12,000 total posts on the forum, >20 individuals currently browsing, and > 10 new posts/day. All posts posted in Jul and Dec 2010 and Feb-Mar 2011 on the two forums were abstracted for review and coding using MaxQDA software. Results: A total of 1,654 posts, posted by 264 individuals, were identified on the two CRC web forums. Demographic and /or tumor information were identified for 83% of the posters. Of these, 83% were CRC patients and 17% were family members; 76% were females, and the mean age of the patients was 49 years. The majority had advanced cancer (44% stage IV or metastatic, 40% stage III). The most common topics were a variety of side effects (62.3% of posts), treatment response (13%), and impact on personal, social, and work lives, income and life styles, and resulting emotional distress (23.9%). The posters came to the online forums in part to have an emotional outlet. Another key motive was sharing experiences and seeking advice. Formal knowledge regarding the likelihood of response, magnitude of benefit, or side effects was absent however, leading to senses of uncertainty, anxiety, sometimes shock, and unrealistic expectations. On balance, although patients reported difficulties being on treatment, they also expressed resilience and appreciation for the availability of treatment options and the hope they provide. Conclusions: Online CRC communities provide patients with convenient and valuable emotional support and disease and treatment information. The profound impact of CRC and treatments goes beyond efficacy, toxicity, and structured quality of life scores. Systematic information and decision tools are needed to minimize uncertainties and help patients manage expectations and emotional distress.