Jeroen Ruwaard was an extraordinary researcher, psychologist and pioneer in online treatment. Very unexpectedly he passed away on the 16th of July 2019. Jeroen is one of the key figures in e-mental health development & research. Being part of the Interapy-team at the University of Amsterdam (UvA), he was responsible for designing the first online treatment platforms, via which thousands of people were treated for psychological problems. As a researcher at the UvA and later at the Vrije Universiteit (VU) and GGZ-Geestgronden, he set the standard for RCT's and naturalistic studies in e-mental health, not only focusing on statistical significance, but also on clinical relevance of results. Jeroen was one of the most lucid thinkers in his field in which he stayed in the forefront, publishing on a wide variety of subjects, ranging from the quality of e-help for children to ecological momentary assessment (EMA) and big-data analysis. We will miss Jeroen incredibly, not only because of his brilliantness, but also because he was one of the most charming and witty people you could meet.