GSQ and University of Groningen jointly held the 4D Treatment Workshop for Particle Therapy 2018 on December 7 and 8 at School of Medicine, Hokkaido University. This workshop has been held annually since 2009 in European countries, and this year marks the 10^th edition. World-leading researchers from MD Anderson Cancer Center, Paul Scherrer Institute, Stanford University, University of Groningen, University Medical Center Utrecht, Sydney Medical School, Ecole Centrale Paris, National Institute of Radiological Sciences, Saga HIMAT, University of Tsukuba, as well as from Hokkaido University gave compelling talks that cover a wide range of aspects of planning and delivery of proton and heavy ion radiotherapy to moving targets. Lively discussions followed each talk, where speakers and participants exchanged their opinions. Poster session was also held during the event and 12 poster presenters had active interaction with the audience on their research. The workshop welcomed 70 participants from 13 countries and regions: Australia, Austria, France, Germany, Italy, Japan, Netherlands, Poland, South Korea, Switzerland, Taiwan, UK, and USA. We hope that the workshop was stimulating, inspirational, and provided great opportunities for the participants to establish connections as well as expand their knowledge. Workshop Official Website: http://4dworkshop2018sapporo.hkdo.jp/index.html