Objective: To explore the epidemic situation of cannabis use among drug users with compulsory detained detoxification treatment in China.Methods: Using the data from the Drug Abuse Population Estimation in the Key Cities of the Ministry of Public Security, we analyzed the sociodemographic characteristics and substance use of cannabis abusers with compulsory detained detoxification treatment in 55 provincial capital cities and key cities of China. Chi-square test, Fisher exact test and Kruskal-Wallis rank sum test were used to compare the prevalence of cannabis, heroin, synthetic and mixed drug use among patients with detoxification treatment, as well as the differences in polydrug use and areas among cannabis users.Results: In the study, 25 366 drug users with compulsory detained detoxification treatment were recruited, of whom 2.2% (546/25 366) used cannabis in the previous year before the treatment. The proportion of males was 83.5%, and the proportion of ethnic minorities was 41.0%. Those who received junior high school education or above accounted for 30.8%, and the unemployed accounted for 44.1%. The average age was (33.3±8.2) years, the average age of beginning drug use was (24.8±7.7) years, and the average duration between the first drug abuse and first detoxification treatment was (5.4±4.6) years. The prevalence of cannabis use was higher among those drug users who were 35-year-old and younger, ethnic minorities, employees and residents in Xinjiang. Of the cannabis users, 91.4% used polydrug, 13.6% combined with heroin alone, 42.1% combined with synthetic drugs alone and 35.7% combined with both of heroin and synthetic drugs. Of the cannabis users, 49.6% came from 3 regions: Xinjiang Uygur Autonomous Region, Jiangsu Province and Shanghai City. The cannabis users in Xinjiang had a high proportion of ethnic minorities who received junior high school education and below. Moreover, 79.6% of them combined cannabis use with heroin. The cannabis users in Jiangsu, Zhejiang and Shanghai areas had a higher proportion of ethnic Han who received better education (high school and above). Moreover, 92.7% of them combined cannabis use with methamphe-tamine.Conclusion: The prevalence of cannabis use among the population with compulsory detained detoxification treatment is higher than that among drug users under surveillance, but there are obvious regional cluster effect and high possibility of polydrug abuse. Thus, it’s important to strengthen the monitoring of cannabis use, to increase the control of cannabis and to formulate China’s anti-cannabis policy among different population.