The data presented in this paper describe trends in treated problem cannabis use in seven health board areas, namely: the Midland, Mid-Western, North Eastern, North Western, Southern, South Eastern and Western Health Boards. The total numbers include 6,164 cases who lived and were treated in the seven health boards between 1998 and 2002. In this paper, treated problem cannabis use is described in relation to person, place and time. This paper will assist policy makers and service planners develop appropriate responses to problem cannabis use. The analysis presented in this paper is based on data reported to the National Drug Treatment Reporting System (NDTRS).