Medical expenses are increasing year by year in Japan. However, the quantity of disposed medical opioids is not well known. In this study, we assessed disposed medical opioids in community pharmacies of Fukuoka city and in all of medical organizations of Kumamoto cities for 3 and 2 years, respectively. We collected official opioid disposal reports in Kumamoto city and Fukuoka City Pharmaceutical Association disposal information sheet in Fukuoka city. The total amount of disposed opioids was worth 7.1 million ¥ from 2017 to 2019 in Fukuoka city, and 8.9 million ¥ in for 2 years (2018 and 2019) in Kumamoto city. In Fukuoka city, the most disposed opioid was 20 mg Oxycontin®, worth approximately 940,000 ¥. In Kumamoto city we assessed data in different organizations. The most disposed opioid was 5 mg Oxinorm® at a cost of 600,000 ¥ at the medical institutions over the 2-year study period. The most disposed opioid was 40 mg Oxycontin®, at a cost of 640,000 ¥ in community pharmacies. Two hundred µg E-fen® buccal tablet was the most disposed of opioid, was amounting to 960,000 ¥ in wholesalers. On the whole in Kumamoto city, non-dispensing was the most common reason of disposal. These results indicate that the amount of disposed opioids is huge. Small package simulation studies suggest that smaller package units of MS-Contin®, Anpec® suppository, and Abstral® sublingual tablet may be able to reduce the amount of disposed opioids.