The role of androgen deprivation therapy combined with heavy ion radiotherapy involving carbon ions was reviewed. In conventional radiotherapy, short- and long-term androgen deprivation therapies were recommended for patients with intermediate- and high-risk prostate cancers, respectively. The rationale for using a combination androgen deprivation therapy can be partially explained by prostatic tissue oxygenation and the effect on DNA-repair molecules via the androgen receptor. Heavy ion radiotherapy and androgen deprivation therapy were performed in combination according to risk criteria. Further studies are warranted to determine the optimal method and duration of androgen deprivation therapy during heavy ion radiotherapy for prostate cancer.