Background: Curative-intent radiation treatment for head and neck cancer (HNC) is painful and often requires opioids. Opioid prescribing patterns and duration are not known for these patients. Identifying patients using high amounts of opioids may permit targeted interventions to reduce overall opioid usage. Methods: This retrospective observational study collected EMR prescription data on 10755 patients with a diagnosis of HNC, along with 15664 patients with a diagnosis of breast cancer (BC), between 2008-2022 at Stanford. We identified every non-IV opioid and adjunctive medicine (e.g. gabapentin) prescription using the Stanford Research Repository (STARR). We analyzed opioid prescriptions in 894 HNC and 1100 BC patients who received definitive or adjuvant radiation for 4-6 weeks, and compared usage by age, gender, and ethnicity. A multivariate logistic regression was used to estimate the odds ratio of prescribing opioids, adjusting for age, gender, race, ethnicity, insurance type, and substance use history. Results: HNC patients prescribed opioids were 69% male; 66% white, 17% Asian; median age of 65.9 years (IQR: 56.9-73.9); 48% prior smokers and 2% reported prior heavy drinking. 774 of 894 HNC radiation patients were ever prescribed opioids. Relative to the start of radiation, the numbers of HNC radiation patients prescribed opioids were: 259 (29%) within < 30 days prior; 355 (40%) within 30 days after; 329 (37%) within 30-60 days after; 142 (16%) within 60-90 days after; 86 (10%) within 90-120 after; 67 (7%) within 120-150 days after; 56 (6%) within 150-180 days after; 53 (6%) within 80-210 days after; 43 (5%) within 210-240 days after. Across all time periods for HNC radiation patients fentanyl (72-83%) and oxycodone (79-85%) were the most common opioid prescriptions, while morphine (14-24%) and hydromorphone (22-27%) were the least common opioid prescriptions. Concurrent gabapentin prescriptions were given to > 80% of HNC patients with opioid prescriptions at every time period, peaking at 91% at the end of radiation. Compared to BC radiation patients, HNC radiation patients had an odds ratio of 3.34 (95% CI: 1.79-6.80, p = < 0.01) in favor of opioid prescriptions and 8.26 (95% CI: 5.74-12.15, p = < 0.01) for adjunctive medicine prescriptions. There was no significant difference between prescriptions by age, race, ethnicity, or prior smoking history. Males compared to females had a lower odds ratio of 0.37 (p = < 0.01) for opioid prescriptions. Conclusions: HNC radiation patients have high rates of opioid and adjunctive medicine prescriptions at our center. Opioids are most prescribed before and during radiation and decrease by > 80% by 6 months after radiation started. 6% of HNC patients still require opioid prescriptions over 6 months after the start of radiation. HNC radiation patients use opioids and adjunctive medicines much more frequently than BC radiation patients.