Changing patterns of addiction and increased psychiatric comorbidity pose new challenges for social services. As part of systematizing the work of assessing and investigating the need for help for people with alcohol or drug problems, use of the Addiction Severity Index is recommended. This descriptive quantitative study examines and compares how social workers and clients esti-mate the extent of a client’s problems in three areas: mental health, alcohol and drugs. Based on interviewer and client estimates, the study also examines whether the problems are estimated dif-ferently over time, from 2003 to 2017. The study includes ASI material for 15,005 people whose need for help for alcohol or drug problems has been investigated and assessed by the social services in 65 Swedish municipalities. The study shows that both clients and social workers estimate an increased problem level for the ASI domains of mental health and drugs. For alcohol, the trend is the opposite or is unchanged. Overall, interviewer as well as client estimates indicate an increased need for help and support for problems related to mental health and drug use, while the need for help and support for problems related to alcohol is unchanged or decreases over time among social service clients.