ABSTRACT: Purpose: Adolescents and young adults (AYAs) with cancer are a vulnerable population with decreased attendance at National Cancer Institute (NCI) comprehensive cancer centers and Children's Oncology Group (COG) facilities. Decreased attendance at NCI/COG facilities has been associated with poor cancer outcomes. The objective of this study was to evaluate cancer care patterns of AYAs compared with children, within Pennsylvania, and factors associated with attending an NCI/COG facility. Methods: Data from the Pennsylvania Cancer Registry between 2010 and 2015 for patients aged 0-39 years at cancer diagnosis were used. Primary analyses focused on age at diagnosis, insurance status, race, ethnicity, gender, cancer type, stage, diagnosis year, and distance to the NCI/COG facility. The primary outcome was receipt of care at an NCI/COG facility. Odds ratios (ORs) were calculated using multivariable logistic regression models. Sensitivity analyses were conducted to test and estimate robustness. Results: A sample of 15,002 patients, ages 0-39, was obtained, including 8857 patients (59%) who attended an NCI/COG facility. Patients were significantly less likely to attend an NCI/COG facility if they were aged 31-39 years (OR 0.054, 95% confidence interval [CI] 0.04-0.07), non-White (OR 0.890, 95% CI 0.80-0.99), Hispanic (OR 0.701, 95% CI 0.59-0.83), female (OR 0.915, 95% CI 0.84-1.00), had Medicaid insurance (OR 0.836, 95% CI 0.75-0.93), and lived further from an NCI/COG facility. Sensitivity analyses largely corroborated the performed estimates. Conclusions: AYAs with cancer in Pennsylvania have disproportionate attendance at specialized NCI/COG facilities across a variety of demographic domains. Enhancing the attendance of AYAs with cancer at these specialized centers is crucial to improve cancer outcomes.