Myelodysplastic syndromes (MDSs) are a heterogenous group of clonal hematopoietic disorders affecting approximately 60,000 people in the U.S. Little information is available regarding how aware MDS patients are of their disease severity, prognosis, and treatment outcomes. Methods. This Internet-based survey assessed patient perceptions regarding these factors, determined differences between patients with higher- and lower-risk disease and between those receiving active treatment and supportive care, and assessed patient-reported outcomes. Results. Among 358 patients (median age, 65 years), the median time since MDS diagnosis was 3 years and time from initial hematologic abnormality detection was 6 years. Many patients (55%) did not know their International Prognostic Scoring System score, 42% were unaware of their blast percentage, and 28% were unaware of their cytogenetics. Patients were unlikely to recall having their MDS described as cancer (7%), 37% felt their treatment would improve survival, and 16% felt treatment would be curative. Patients receiving active treatment were more likely to believe their therapy would prolong survival than those receiving supportive care (52% versus 31%; p < .001) or be curative (23% versus 14%; p = .03). Patients with higher-risk disease were more likely to think their therapy would be curative than those with lower-risk disease (26% versus 11%; p = .01). Patients with MDS reported poor physical or mental health on two to three times more days per month than population norms. Conclusion. Patients with MDS have a limited understanding of their disease characteristics, prognosis, and treatment goals. These results may help improve physician-patient communication and identify factors to consider when making treatment decisions.