We hypothesized that breast cancer (BCa) patients in urban counties would have higher rates of post-lumpectomy radiation therapy (RT) relative to patients in near-metro and rural counties. We used the Surveillance, Epidemiology, and End Results (SEER) database to identify women diagnosed with BCa treated with lumpectomy in the Sacramento area between 2000 and 2006. Patient counties were categorized as urban and near-metro. Multivariate logistic regression models predicted treatment with RT. Likelihood of undergoing RT was reported as odds ratios (OR) with 95 % confidence intervals (CI). Of 7,953 patients meeting entry criteria, 5,858 (73.7 %) underwent RT. On multivariate analysis, patients from near-metro (OR, 0.66; CI, 0.59-0.75; P < 0.001) and rural (OR 0.39, CI 0.30-0.52; P < 0.001) areas had a decreased likelihood of undergoing RT relative to patients from urban areas. Patients from near-metro and rural areas are less likely to receive RT following lumpectomy for BCa than their urban counterparts.