153 Background: Symptoms are prevalent among cancer patients, but little is known about how often patients’ needs for symptom management are met or what factors are associated with unmet needs. Methods: Patients with lung and colorectal cancer from the diverse nationally-representative Cancer Care Outcomes Research and Surveillance cohort completed a survey approximately 4-6 months following diagnosis (n=5,422). We estimated the prevalence of unmet needs for symptom management during the 4 weeks prior to the survey, with unmet needs defined as patients reporting that they wanted but did not receive help for at least one symptom (pain, fatigue, depression, nausea/vomiting, cough, dyspnea, diarrhea). Using a pre-specified conceptual model, we identified patient factors associated with unmet need using multivariable logistic regression with random effects (fixed slopes model with random intercepts for each Primary Data Collection Research site). We also tested whether clinical visits before the interview were associated with unmet need. Results: Overall, 15% (791/5,422) of patients had at least one unmet need for symptom management. Adjusting for patient sociodemographic and clinical factors, African American race, being uninsured or poor, having lung cancer versus colorectal cancer, early- vs. late-stage disease, and the presence of moderate to severe symptoms were associated with greater unmet need (all p<.05). Patients who rated their physicians communication score below 80 (on 1-100 scale) had adjusted rates of unmet need that were more than twice those of patients who rated their physicians with a perfect communication score (23.0% v. 10.0%, OR=3.05, p<0.001). Neither visits with specialty physicians (medical oncology, radiation oncology, surgery, or primary care) nor the total number of outpatient visits in the 28 days before the interview were associated with unmet need (all p>.05). Conclusions: A significant percentage of newly diagnosed lung and colorectal cancer patients report unmet needs for symptom management. Interventions to improve symptom management should consider the importance of physician communication to the experience of disease.