Drug abuse is a critical issue impairing social welfare in many societies. This study explores the demographic characteristics of drug abuse among sub-populations in Hong Kong as a developed and ageing society with large socioeconomic disparities. Significant changes in both the number and rate of drug abuse by drug type, age, gender, ethnicity, education and economic activity are documented during 1991 to 2016. Although narcotics analgesics is more common, stimulants and Ketamine are growing popular in Hong Kong, especially among the youth. The number of elderly drug abusers is increasing due to the ageing population, whereas the rate of elderly drug abuse is actually stable or decreasing. In contrast, drug abuse rate is increasing for the middle-aged and for groups with lower education. The findings support social policy design to curb drug abuse, and call for closer attention to these at-risk groups that are overlooked in Hong Kong.