Recent changes in the Swiss gambling context include the introduction of a new gambling policy (Swiss Federal Act on Gambling; GA), and the associated opening of the online gambling market. Within this context it is important to observe evolving trends in gambling behavior. This study therefore aims to identify the gambling behavior and clinical characteristics of a treatment-seeking population over an 18-year period (2001 to 2018). Specifically, the proportion of referrals relating to the three most popular game-types; VLT play, slot machines and online gambling, and associated socio-demographic characteristics, gambling-related spending and clinical features. The results indicate the high addictive potential for VLT and slot-machine use, over the 18-year period with an increasing use of online gambling from 2012 to 2018 (even before the official opening of the market). Problem-gambling vulnerability factors such as low income, unemployment and debts as well as self-reported suicidal ideation, were also over-represented in the sample. This longitudinal overview provides a detailed picture of treatment-seeking referrals, for future comparisons and can be used to tailor clinical interventions.