Background: Orbital adenocarcinoma is a relatively rare, primary orbital malignant epithelial tumor, and shares the poor prognosis of orbital adenoid cystic carcinoma.We report the cases of two patients with orbital adenocarcinoma who were treated with heavy charged carbon particle irradiation and followed up for more 6 years. Method: Two patients with orbital adenocarcinoma, 62 and 74 years old, received 57.6 GyE of heavy charged particle irradiation therapy. Results: In both cases, the size of the tumor gradually decreased after carbon ion irradiation therapy. No recurrences or metastasis of the tumor were found for more than 6 years. Conclusion: Orbital adenocarcinoma has a poor prognosis in general. Two patients with orbital adenocarcinoma were treated with heavy charged carbon particle irradiation therapy and had a relatively good outcome and good prognosis. We believe that heavy charged carbon particle irradiation therapy is a promising therapy for orbital adenoud cystic carcinoma and adenocarcinoma